Few cards short of a full deck derogatory slang
If you say that someone is a few cards short of a full deck, you mean they are quite silly or mentally abnormal.
I thought he was a few cards short of a full deck when he told me to make money from selling fart!
I didn't allow John to join my team as I thought he was a few cards short of a full deck.
Every time he dances like that, I can't help thinking he is a few cards short of a full deck.
Extremely stupid
Very stupid, or silly
Stupid or crazy
(n): a fool person,
(adj): stupid, foolish, silly
The origin of this slang is not clear.