noun
in the palm of one's hand; within one's grasp
Literally inside one's hand; figuratively, something fully under one's control or easily manipulated. Often used in set phrases like 掌中に収める.
彼は会社を完全に掌中に収めている。
He has the company completely in the palm of his hand.
その秘策で、彼は敵を掌
With that secret plan, he had the enemy in his grasp.