Domino/ˈdɑːmɪnəʊ/ Definition 1 of 4Pro Tip 1/2Game Piece Used mostly in the game context; avoid using it to refer to pieces in other contexts like puzzles. Who knocked over the dominoes? Pro Tip 2/2Counting Dots Each half's dots range from none (blank) to six, important for game rules. This domino has five dots on one end and three on the other.