Definition of bet:
, an agreement between two parties that a stake (usually money) will be paid by the loser to the winner the one who correctly forcast the outcome of an event; a degree of certainty
"it's a good bet that it will rain tomorrow."
to agree that payment be made to the successful forecaster of the result of an event (usually sporting) by the other party in the agreement. To make a guess
about the outcome
of an event; to be sure
of something; to be able to count