Mac prop. n. Shortened form of Macintosh, a brand name for a personal computer; as, the latest Mac has great new features.[PJC]
Mac (?). [Gael., son.] A prefix, in names of Scotch origin, signifying son.[1913 Webster]
mac n. Shortened form of mackintosh, a waterproof raincoat made of rubberized fabric.Syn. -- mackintosh, mac, mack.[WordNet 1.5]