Define bet (verb) and get synonyms. What is bet (verb)? bet (verb) meaning, pronunciation and more by Macmillan Dictionary. Bet definition, to wager with (something or someone). See more. s. Meaning yes or I agree. as in "sure," "you bet," "you know it," "thats for sure," "thats a plan," or "i will do it". Hey, lets go to the zoo tomorrow! Aight, bet!.