"not playing with a full deck"

readok2009

Meaning: stupid, not intelligent, dumb/idiotic

Example: Johnny is clearly not playing with a full deck... He didn't even
study for this test!

Origin: it used to be that to make games easier for children, certain cards
are not used in card games. Later, it's became an expression to describe
someone who's \"not all there\".

Similar expressions... lots of them. You can probably invent a few by
following some of these... Just make sure it's obvious.

\"Jim, I don't think he's firing on all thrusters.\"
\"Tony clearly isn't firing on all cylinders.\"
\"Liam's mom is old... her elevator doesn't go all the way to the top, if
you know what I mean...\"