Bet (archaic) used to mean to wager against someone that you are right and the are wrong.
Or can mean that something is definitely true when both parties are in agreement.
Wana bet?
Bet me.
Safe bet.
I bet you're right.
A response when someone thinks you won’t do something, but you will.
You: “My guy will not eat that puke!”
Me: “Bet”
Sarcastic but a real response to accepting a challenge, any kind of challenge.
*person doesn’t respond to texts or calls
Me: so we not speaking today?
No response—
*calls person
Me again: bet
Me: oh we forwarding calls now?
Me: bet
A reply to a challenge or statement undermining the person, a shortening of "Do you want to bet?" it can be simplified to "Is that a challenge" or "Really? Watch this."
1: "You are way too short to touch the cieling here!"
2: "Oh, bet!" (you wanna bet? / is that a challenge?)