The Collaborative International Dictionary of English v.0.48:
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. [1913 Webster]WordNet (r) 3.0 (2006):
square-rigged adj 1: rigged with square sails as the principal ones