Origin: 1000-1100 Old North French castel, from Latin castellum building with a defensive wall
1 a very large strong building, built in Europe in the past as a safe place that could be easily defended against attack2one of the pieces used in a game of chessSYN rook3build castles in the air to make plans or imagine things that are unlikely ever to become realSYN daydream [Origin: 1000–1100 Old North French castel, from Latin castellum building with a defensive wall]