The Collaborative International Dictionary of English v.0.48:
halftime \half"time`\ n. an intermission between the first and second half of a game, especially a football game. Also used attributively, as the halftime entertainment [WordNet 1.5 +PJC] Half toneWordNet (r) 3.0 (2006):
halftime n 1: an intermission between the first and second half of a game