n. (pl. -oes) 1 a any of 28 small oblong pieces marked with 0-6 pips in each half. b (in pl., usu. treated as sing.) a game played with these. 2 a loose cloak with a mask for the upper part of the face, worn at masquerades. domino theory the theory that a political event etc. in one country will cause similar events in neighbouring countries, like a row of falling dominoes.
[ F, prob. f. L dominus lord, but unexplained ]