n., adj., & v.
n. (pl. -ies) 1 a model of a human being, esp.: a a ventriloquist's doll. b a figure used to model clothes in a shop window etc. c a target used for firearms practice. 2 (often attrib.) a a counterfeit object used to replace or resemble a real or normal one. b a prototype, esp. in publishing. 3 colloq. a stupid person. 4 a person taking no significant part; a figurehead. 5 Brit. a rubber or plastic teat for a baby to suck on. 6 an imaginary fourth player at whist, whose hand is turned up and played by a partner. 7 Bridge a the partner of the declarer, whose cards are exposed after the first lead. b this player's hand. 8 Mil. a blank round of ammunition. 9 colloq. a dumb person.
adj. sham; counterfeit.
v.intr. (-ies, -ied) Football make a pretended pass or swerve etc. dummy run 1 a practice attack, etc.; a trial run. 2 a rehearsal. dummy up US sl. keep quiet; give no information. sell the (or a) dummy Rugby Football colloq. deceive (an opponent) by pretending to pass the ball.
[ DUMB + -Y(2) ]