What does "Shorting a stock" mean

SEC calls it "Short Sale" of a stock but you'll hear people say "I'm shorting this stock". Its a little complicated to understand what shorting means but keep in mind that you short sell a stock when you believe the stock price will fall. To understand what it means from the mouth of the river, read it yourself at http://www.sec.gov/answers/shortsale.htm.

SEC puts restrictions on Short Selling stocks. Those restrictions can be read at http://www.sec.gov/answers/shortrestrict.htm.