v. & n.
v. (betting; past and past part. bet or betted) 1 intr. (foll. by on or against with ref. to the outcome) risk a sum of money etc. against another's on the basis of the outcome of an unpredictable event (esp. the result of a race, game, etc., or the outcome in a game of chance). 2 tr. risk (an amount) on such an outcome or result (bet $10 on a horse). 3 tr. risk a sum of money against (a person). 4 tr. colloq. feel sure (bet they've forgotten it).
n. 1 the act of betting (make a bet). 2 the money etc. staked (put a bet on). 3 colloq. an opinion, esp. a quickly formed or spontaneous one (my bet is that he won't come). 4 colloq. a choice or course of action (she's our best bet). you bet you may be sure.
[ 16th c.: perh. a shortened form of ABET ]