castle

¹ American  

[kas-uhl, kah-suhl] / ˈkæs əl, ˈkɑ səl /

noun

1. a fortified, usually walled residence, as of a prince or noble in feudal times.

   Synonyms:

   citadel, fortress

2. the chief and strongest part of the fortifications of a medieval city.

3. a strongly fortified, permanently garrisoned stronghold.

4. a large and stately residence, especially one, with high walls and towers, that imitates the form of a medieval castle.

   Synonyms:

   château, palace

5. any place providing security and privacy.

   It may be small, but my home is my castle.

6. Chess. the rook.

---

verb (used with object)

castled, castling

1. to place or enclose in or as in a castle.

2. Chess. to move (the king) in castling.

verb (used without object)

Chess.

castled, castling

1. to move the king two squares horizontally and bring the appropriate rook to the square the king has passed over.

2. (of the king) to be moved in this manner.

Castle ² American  

[kas-uhl, kah-suhl] / ˈkæs əl, ˈkɑ səl /

noun

1. Irene (Foote), 1893–1969, born in the U.S., and her husband and partner Vernon (Vernon Castle Blythe ), 1887–1918, born in England, U.S. ballroom dancers.

---

castle British  

/ ˈkɑːsəl /

noun

1. a fortified building or set of buildings, usually permanently garrisoned, as in medieval Europe

2. any fortified place or structure

3. a large magnificent house, esp when the present or former home of a nobleman or prince

4. the citadel and strongest part of the fortifications of a medieval town

5. chess another name for rook 2

---

verb

1. chess to move (the king) two squares laterally on the first rank and place the nearest rook on the square passed over by the king, either towards the king's side ( castling short ) or the queen's side ( castling long )

Other Word Forms

• castlelike adjective
• uncastled adjective

Etymology

Origin of castle

before 1000; Middle English, Old English castel < Latin castellum castellum

Example Sentences

It looked like a castle on the hill.

From The Wall Street Journal • Mar. 29, 2026

Tuesday, OpenAI announced it was abandoning its video-production aspirations, giving Disney a graceful exit until the next model storms the castle.

From Salon • Mar. 26, 2026

They insist the castle will allow them the "opportunity to create a truly unique experience and elevate the show to the next level for everyone attending".

From BBC • Mar. 16, 2026

The looming castle complex that watches over the city contains the mark of almost every era since its original construction in the Middle Ages.

From The Wall Street Journal • Mar. 13, 2026

There is a grand stone castle in the distance behind her, and she is dashing toward the rustic stables.

From "The Sea in Winter" by Christine Day