The Collaborative International Dictionary of English v.0.48:

Castle \Cas"tle\, v. i. [imp. & p. p. Castled; p. pr. & vb. n.
   Castling.] (Chess)
   To move the castle to the square next to king, and then the
   king around the castle to the square next beyond it, for the
   purpose of covering the king.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Castled \Cas"tled\, a.
   Having a castle or castles; supporting a castle; as, a
   castled height or crag.
   [1913 Webster]

   2. Fortified; turreted; as, castled walls.
      [1913 Webster]

WordNet (r) 3.0 (2006):

castled
    adj 1: having or resembling repeated square indentations like
           those in a battlement; "a crenelated molding" [syn:
           embattled, battlemented, castled, castellated]