Etymology: Middle English lucke, from Middle Dutch luc, short for gheluc.
1: A fictional creation used to explain random events when a rational explanation is lacking. Man, I'm so unlucky that a meteorite hit a plane on entering the atmosphere, knocking a hole in its fuselage just big enough to suck a midget acrobat out, who crashed through my roof and smashed the television, just as I was sitting down to watch Lost.
2: A misapplication and/or misunderstanding of mathematics. Man, I was flipping a quarter yesterday and some guy in a clown suit wandered into my living room and told me he'd give me $73 and a blowjob if I could flip heads eighteen times in a row, and I was sooooooo lucky, and flipped heads eighteen times in a row! The odds of that happening are astronomical so I must be the luckiest human on earth!
3: A psychological coping mechanism, most often invoked when facing adversity or setbacks. I guess if there were no luck, I’d win every one.