a keyboard error made by a securities trader who pushes the wrong key or keys when entering a trade.
In a day short of major U.S. data, the bond market was jolted during the midmorning session as talk circulated in the market that an investor made a mistake—known as a "fat finger" error—on a trade inquiry, according to several traders and dealers. . . .[A]n investor intended to sell $6 million in 10-year Treasury notes but mistakenly put an inquiry of $6 billion to some dealers. The error was spotted and the trade didn't go through, according to the primary dealers. . . .
"Fat finger" trade typically means a trader pushes a wrong key or sequence of keys.