Three wickets taken by a bowler in three consecutive balls.
Three goals scored by one player in a game, in ice hockey usually followed by fans throwing their hats onto the rink.
After Jones' hat trick, the attendents had to pick up about 75 hats from the ice.
(by extension) Three achievements in a single game, or similar, such as three consecutive wins.
A "Gordie Howe hat trick" comprises a goal, an assist, and a fighting major penalty.
Striking out three times in one game.
Jones got a hat trick yesterday. Let's see if he can do something today.
(by extension) Three incidents or achievements that occur together.
(UK politics) A means of securing a seat in the House of Commons by placing one's hat upon it.
Any magic trick performed with a hat.