Justin Sullivan / Getty Images

U.S. Postal Service worker Magda Aguirre places mail into a sorting machine at the U.S. Post Office sort center in San Francisco, Calif., last August.

Staff reductions. Job cuts. Layoffs. Right-sizing. Restructuring.

Euphemisms for firing workers have become painfully commonplace in recent years, as all sorts of employers have eliminated jobs to deal with the recession and weak economic recovery.

Plenty of big companies have led the way with massive layoffs, but the organization that has announced the largest reductions over the past five years may surprise you. It’s Uncle Sam.

Msnbc.com asked outplacement firm Challenger, Gray & Christmas to compile a list of the employers that have publicly announced the most job cuts from the beginning of 2007 through the end of 2011. Challenger relies on public announcements and news reports to compile its data and checks those against government-mandated layoff notices when available.

The U.S. government topped the list with 112,800 job cuts announced over the past five years, mainly at the U.S. Postal Service and in the defense sector.

The government tops the list in part because it’s the nation’s largest employer. The government employed about 2.8 million workers as of January, so the announced job cuts would have amounted to only about 4 percent of the total.

Despite those announced job cuts, total federal employment is about the same today as it was in 2007. Employment did increase in 2010 and then fell again, possibly a result of the decennial census.

At the Postal Service, the story is different. Postal Service employment has dropped by 148,000 over five years to the current  618,000, according to the Bureau of Labor Statistics.

The Post Office’s woes come down to two words:

“The Internet,” said Mike Montgomery, an economist with IHS Global Insight who watches employment trends closely.

Thanks to the Web, billions of bills, letters and other correspondence that once flowed through the Postal Service are now being sent electronically, leading to billions of dollars in losses. The post office has said the job cuts have helped save some money.

The Department of Defense also is girding for big changes as it works to withdraw troops from Iraq and Afghanistan. Defense spending may be cut by as much as $487 billion over 10 years.

Even if you don’t want to work for the Post Office or Defense Department, the prospect of making a career with the federal government may be waning. The Labor Department projects that federal government employment will shrink by 372,000 jobs by 2020.

“There aren’t a lot of places where either Congress or the White House wants to spend more money on payroll,” said Montgomery, of IHS Global Insight,.

That’s a remarkable turnaround from past years, said John Challenger, chief executive of Challenger, Gray and Christmas.

“Government was the last bastion of job security,” he said.

After the government, General Motors is No. 2 on the list of employers that have announced the most job cuts in the past five years, according to Challenger.

Note: The number of job cuts announced is rarely the same as the number of jobs actually eliminated. Companies may end up firing workers in some divisions but hiring workers elsewhere. Fortunes shift, and plans can change. But announced job cuts usually lead to real pain.

Here are the rest of the top 10:

2. General Motors

Announced job cuts: 112,700

Employees: 202,000 employees as of December 31, 2010

General Motors filed for bankruptcy protection in 2009, after years of problems at the giant automaker.

Aided by the government, it emerged quickly from bankruptcy and has since staged a recovery and return to profitability.

General Motors had about 280,000 employees as of December 2006, and employment had fallen to 196,000 by March of 2010, according to spokesman Jay Cooney.

As the company's fortunes have improved, it’s started adding workers again. Cooney said GM added 6,000 jobs through the end of 2010, all in the United States. The company continued to add jobs in 2011, he said, but he wasn’t able to provide a firm number.

3. Citigroup

Job cuts announced: 96,500

Employees: 260,000 as of December 2010

As early as 2007, Citigroup was hit hard by the housing bust and the credit crisis. The banking giant received $45 billion in government aid in late 2008, as part of the government bailout plan, and the government later took a stake in the bank. The Treasury Department has since sold all shares, making a profit on the deal.

At its height in late 2007, Citigroup employed 375,000 people, spokeswoman Shannon Bell said. The company’s workforce has fallen by more than 100,000 as it has shed some businesses and lost staff through layoffs and attrition.

Citigroup continues to struggle amid slow growth in the United States and economic problems abroad.

4. Hewlett-Packard Co.

Announced job cuts: 45,300

Employees: 349,600 as of Oct. 31, 2011

Technology giant Hewlett-Packard Co. had 172,000 employees as of October 2007, but several big acquisitions pushed employment up substantially. The company had approximately 320,000 employees in late 2008, when it announced plans to eliminate about 24,600 workers, or 7.5 percent of its workforce, following its acquisition of EDS.

Still, the company’s total employment has risen in recent years. HP spokesman Michael Thacker said that’s partly because of acquisitions and partly because of investments in emerging fields, such as cloud computing.

Thacker declined to comment on the total number of layoffs provided to msnbc.com by Challenger, Gray and Christmas.

5. Circuit City Stores

Announced job cuts: 41,305

Employees: 0

After struggling for years, electronics retailer Circuit City finally closed its doors for good in 2009. The bankruptcy liquidation resulted in hundreds of retail locations closing and all the retailer’s employees losing their jobs.

Another company, Systemax, later bought the rights to Circuit City’s website and brand name. A spokesman with Systemax’s public relations firm, Brainerd Communicators, said the company had no employees left when Systemax purchased the intellectual property.

6. Bank of America

Announced job cuts: 41,000

Employment: 281,791 as of Dec. 31, 2011

Bank of America was among the many companies to receive government bailout funds following the 2008 financial crisis. The company was able to repay the $45 billion it owed taxpayers in 2009, but it has continued to struggle.

Bank of America, which acquired both mortgage lender Countrywide Financial and wealth management firm Merrill Lynch in recent years, has been slashing jobs and costs in an effort to rein in its unwieldy size. Last fall, the company said it planned to cut up to 30,000 positions over the next several years.

Bank of America had 203,425 employees as of Dec. 31, 2006, and that number swelled to 288,128 by the end of 2010 in large part because of acquisitions. It has since fallen somewhat.

7. Merck & Co.

Job cuts announced: 36,500

Employees: 86,000 as of Dec. 31, 2011

Pharmaceutical giant Merck bought Schering-Plough in 2009 in a deal that was aimed at helping boost its business but also led to job cuts.

The maker of Gardasil and other drugs has said it expects its restructuring program, which includes cost-cutting and staff reduction, to continue until 2015.

The combined companies had 100,000 workers at the time of the 2009 merger, spokesman Ron Rogers said. Rogers added that Merck has been cutting jobs in some areas of the business while boosting employment in others.

8. Merrill Lynch

Job cuts announced: 35,000

Employees: Not available -- acquired by Bank of America

Merrill Lynch was bought by Bank of America at the height of the financial crisis in 2008. At the time, Bank of America said it expected to cut around 35,000 jobs.

9. Pfizer

Job cuts announced: 33,025

Employees: 103,700 as of Dec. 31, 2011

Pfizer, maker of blockbuster drugs such as Viagra and Lipitor, acquired pharmaceutical company Wyeth in 2009. The deal brought Pfizer valuable assets such as Wyeth’s Prevnar vaccine but also led to more job cuts at the combined companies.

In its 2010 annual report, the company said cost-cutting initiatives that started in 2005 are expected to reduce the company’s workforce by about 49,000 employees, mainly in manufacturing, sales and research. The company said 36,400 jobs had been cut by Dec. 31, 2010.

A spokeswoman said by email that the company had about 86,600 employees as of Dec. 31, 2007, and that number swelled to 130,000 by January 2009, when Pfizer acquired Wyeth.

It has since fallen by about 27,000. The company declined to comment further.

10. Chrysler

Job cuts announced: 26,500

Employees: 57,160 as of January 2012

Chrysler filed for bankruptcy protection in 2009 with a plan to quickly emerge from bankruptcy court free of debt and ready to make some hard decisions to save its floundering auto business.

The plan included an alliance with Fiat and a stringent plan to cut some car models and revitalize others.

Many expected it to be an uphill battle. But over the past two years, Chrysler has seen its fortunes improve substantially and  recently handed out its first profit-sharing checks in years.

Chrysler had 82,284 employees as of January 2007, and that figure had fallen to 47,784 by June of 2009. Spokesman Michael Palese said in an email that the company has added about 10,000 employees since then as business has improved.

Discuss the job market on our Facebook page.