Source : Webster's Revised Unabridged Dictionary (1913)

Square-rigged \Square"-rigged`\ (skw[^a]r"r[i^]gd`), a. (Naut.)
   Having the sails extended upon yards suspended horizontally
   by the middle, as distinguished from fore-and-aft sails;
   thus, a ship and a brig are square-rigged vessels.

Source : WordNet®

square-rigged
     adj : rigged with square sails as the principal ones