Basically being sexual to someone, or it could
mean you're an IMPASTA but if you're on
discord, it most commonly means you being sexual, for example:
Me: Hey avi, adam was being kinda sus to me yesterday.
Avi: Huh? what did he say?
Me: Well i
said "gimme cake" and he
said "aww but you're already
sweet enough"
Avi: Ooooo~ i ship