noun

castle

KAH-suhl

noun

A large fortified building, historically home to a king or noble, built to withstand attack.

"Tourists climbed the hill to see the medieval castle."

"The castle walls were over three metres thick."

In chess, a rook, the piece shaped like a tower.

"She moved her castle across the board to threaten his king."

verb

In chess, to make a special move where the king and a rook swap positions under certain conditions.

"He castled early to get his king to safety."

How to Use Castle

Learner’s notes

In plain EnglishA grand fortified building from history, or (in chess) the rook piece and the move that repositions it with the king.

Common mistake

In chess, "castle" as a verb refers to the special king-and-rook move, not simply moving the rook piece on its own.

Common pairings

a medieval castle castle walls castle on the queenside

castled past tense, castles plural, Castles plural, castles singular

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Tourists climbed the hill to see the medieval _____.

From Old English castel, borrowed from Latin castellum, "small fort" — itself a diminutive of castrum, "fort or camp."

Newcastle Hardcastle