I. ˈka-səl noun
Etymology: Middle English castel, from Old English, from Old French & Latin; Old French dialect (Norman-Picard) castel, from Latin castellum fortress, diminutive of castrum fortified place; perhaps akin to Latin castrare to castrate
Date: before 12th century
1.
a. : a large fortified building or set of buildings
b. : a massive or imposing house
2. : a retreat safe against intrusion or invasion
3. : rook III
[
castle 1a: 1 fortified approach, 2 moat, 3 drawbridge, 4 ward, 5 angle tower, 6 donjon or keep, 7 chapel, 8 gallery
]
II. verb
( cas·tled ; cas·tling ˈka-s(ə-)liŋ)
Date: 1587
transitive verb
1. : to establish in a castle
2. : to move (the chess king) in castling
intransitive verb
: to move a chess king two squares toward a rook and in the same move the rook to the square next past the king