All there

Pro Tip 1/3

Use it to comment on someone's mental clarity or alertness, usually implying a lack.

After his sleepless night, Jim didn't seem all there at the meeting.

Pro Tip 2/3

It's often used not to directly call someone insane but to hint at it tactfully.

I wouldn't trust her judgement; she isn't quite all there.

Pro Tip 3/3

This phrase is commonly used in negative sentences to politely state someone is mentally off.

He's not all there ever since the incident.