The Collaborative International Dictionary of English v.0.48:
major suit \major suit\ n. (Bridge) A suit of playing cards which has higher scoring value; specifically, either spades or hearts. Contrasted with a minor suit, being either diamonds or clubs. [WordNet 1.5 +PJC]WordNet (r) 3.0 (2006):
major suit n 1: (bridge) a suit of superior scoring value, either spades or hearts