risk a sum of money or valued item against someone else's on the basis of the outcome of an unpredictable event such as a race or game

he bet on baseball games

I would be prepared to bet that he wanted to leave

most people would bet their life savings on the prospect

used to express certainty

I bet this place is really spooky late at night

he'll be surprised to see me, I'll bet

an act of betting a sum of money

she had a bet on the Derby

for a bet he once rode 200 miles in nine hours