threepeat = three + repeat
Threepeat is the act of doing something a third time, and it's normally reserved for competitors in sporting events. NBA coach Pat Riley submitted a trademark application in November 1988 for the use of three-peat on shirts, jackets and hats.
Threepeat is also one of the most annoying sports cliches out there, in my opinion. I prefer hat trick, and I don't even like hockey!