all there

adjective

Definition of all there

1 : in full possession of one's mental faculties : sane behaved in such a way as to make one wonder if he was quite all there —not often in formal use
2 slang : alert and well informed : quick-witted wide-awake, alert, all there; he knows just where he is and what he means and where he is going — Times Literary Supplement

First Known Use of all there

1821, in the meaning defined at sense 2

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