all there

adjective

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

Word History

First Known Use

1821, in the meaning defined at sense 2

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