witty and knowing; not to be underestimated; smooth operator
Idiomatic expression describing a person who is surprisingly capable, shrewd, or charming, often in a social or worldly sense. Literally 'cannot be put in a corner', implying they are too sharp to be overlooked.
He's a witty and knowing person who always tells interesting stories.
That new employee is not to be underestimated. I hear they've already landed an important client.