ticktacktoe

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. A game played by two people, each trying to make a line of three X's or three O's in a boxlike figure with nine spaces.

Wiktionary

1. n. alternative spelling of tic-tac-toe.

WordNet 3.0

1. n. a game in which two players alternately put crosses and circles in one of the compartments of a square grid of nine spaces; the object is to get a row of three crosses or three circles before the opponent does