bet meaning, definition, what is bet: to risk money on the result of a race, g: Learn more. This Slang page is designed to explain what the meaning of bet is. The slang word / phrase / acronym bet means . Online Slang Dictionary. Define bet: an agreement in which people try to guess what will happen and the person who guesses wrong has to give something — bet in a sentence. Men In Black Mint In Box. English English American Business. Your best bet would be to sell the shares. Predicting things and intuition. Your best bet is to make reservations ahead of time. He made a bet with his brother that he could finish his chores .