It originated in 2000 around South Gwinnett in Georgia and it means "Definitely" or "Im excited" or "I can't wait"or "For sure" or "Cool beans" or "Im down" or "Im game" or "I will be there" or "Yes" or as an updated version of saying "You bet" or "You betcha" which means you agree and are looking forward to an upcoming event/plans of some sort.
Dude: Are you coming to the club tomorrow night? They said Usher is performing and there will be hella chicks there"
Dude 2: Fuck yeah bet that up!
Dude 2: Fuck yeah bet that up!
by RCCola11581 August 18, 2023
Get the Bet that upmug. When you make a bet in poker but you're not sure whether it's a value bet or a bluff. Generally a bad idea.
by PhotonZ July 22, 2024
Get the Schrodinger's betmug. 
by Cswmcwipwsohm February 29, 2020
Get the Always bet on gay.mug.