A "hat-trick" in football usually denotes the scoring of three goals in a single game by a footballer. The goals need not come one after the other, that is, if Player X scores three goals in a game but his teammate Player Y scores a goal that comes between the time Player X scores his second and third goal, then also it is slated to be a hat-trick.
There are certain variations of the defination of hat-trick though. "Flawless (or German) hat-trick" implies scoring all the three goals consecutively. "Perect hat-trick" means scoring one goal with each foot and one with a header.
The scorer of the hat-trick in a football match usually keeps the ball as a personal souvenir as scoring hat-tricks in football matches is not very easy.
The world record for the fastest hat-trick is held by former Ross Country footballer Tommy Ross, who scored three goals in the space of 90 seconds, against Nairn County in Victoria Park in 1964.