bet / bet/ • v. (bet·ting; past bet or bet·ted) 1. [intr.] risk something, usually a sum of money, against someone else's on the basis of the outcome of a future event, such as the result of a race or game: betting on horses I would be prepared to bet that what he really wanted was to settle down [tr.] most people would bet their life savings on this prospect. ∎  [tr.] risk a sum of money against (someone) on the outcome or happening of a future event: I'll bet you $15 you won't find a single scratch. 2. inf. feel sure: I bet this place is really spooky late at night he'll be surprised to see me, I'll bet.• n. an act of risking a sum of money in this way: every Saturday she had a bet on the horses. ∎  a sum of money staked in this way: the bookies are taking bets on his possible successor. ∎  inf. a candidate or course of action to choose; an option: your best bet is to call a professional exterminator. ∎  (one's bet) inf. an opinion, typically one formed quickly or spontaneously: my bet is that the president will veto the bill.PHRASES: all bets are off inf. the outcome of a situation is unpredictable.don't (or I wouldn't) bet on it inf. used to express doubt about an assertion or situation: he may be a suitable companion—but don't bet on it.want to (or wanna) bet? inf. used to express vigorous disagreement with a confident assertion: “You can't be with me every moment.” “Want to bet?”you bet inf. you may be sure; certainly: “Would you like this piece of pie?” “You bet!”