To
do something really badly. "To stink" means to do badly, "joint" here means a place. "Stink up the joint" is an
exaggerated form
meaning you "stink" so badly the whole place starts to stink, as if you've taken a shit.
"Oh no, Magnus! He blundered and lost his Queen! Okay, now I don't
feel bad about my awful last game! Magnus is also
stinking up the joint just like me today!" --
Hikaru Nakamura, on a stream in an online chess tournament, 13.11.2025