noun
tactician; schemer; resourceful person
Can be neutral (a clever strategist) or slightly negative (a cunning schemer), depending on context. Often used in political or business settings.
彼は選挙戦で巧みな策士ぶりを発揮した。
He showed his skill as a tactician during the election campaign.
あの男はただの策士で、信用できない。
That man is just a schemer; I can't trust him.
Compound of 策 (plan, scheme) and 士 (person of a certain profession). The exact historical derivation is uncertain, but the word has been used since at least the Edo period to refer to a person skilled in devising strategies.