to risk money on a race or an event by trying to predict the result

used to say that you are almost certain that something is true or that something will happen

You can bet (that) the moment I sit down, the phone will ring.

I'm willing to bet (that) the analysts will be wrong.

I’ll bet you (that) he knows all about it.

an arrangement to risk money, etc. on the result of a particular event; the money that you risk in this way

an opinion about what is likely to happen or to have happened

My bet is that they've been held up in traffic.

LEARNit Dictionary