The Slap Bet Share definition Flag From the iconic show How I Met Your Mother: If one loses a bet they can choose 10 slaps at the moment or 5 slaps that can be used at any time. If you lose you have to choose one of the options from the Slap Bet. The Slap Bet by mrstealyogirl June 10, 2018 Get the The Slap Bet mug.