1. Drawing unwanted attention to a clandestine activity, usually an illegal one.
2. Lacking respect or awareness of social norms by drawing attention to dynamics that are typically left unspoken.
1. Can you stop being so hotboy while smoke this spliff? You're making it hot.
2. Remember when she pointed out how the bathroom smelled after Jake pooped during the dinner party? That was so hotboy.
A threatening admonishment, directed at an adversary, that the "that" in question will turn an argument physical.
don't do that.