What it means
When something has you weak, it means you're laughing so hard your whole body just gives up for a second. You're folded, wheezing, maybe sliding off the sofa, fully taken out by how funny it is. It's big exaggeration, but in real use it's one of the strongest ways to say something absolutely finished you with laughter.
Usage examples
"His impression of the teacher had me weak."
"Stop, I am weak, I cannot breathe."
"That video of your uncle trying to moonwalk has me weak."
"Nah, the way she said it had us all weak in the group chat."
Where it comes from
From weak, drained of all strength, used to describe being left helpless and floppy with laughter.
