The Collaborative International Dictionary of English v.0.48:
bull-necked \bull"-necked`\, a. Having a short, thick and muscular neck like that of a bull. --Sir W. Scott. [Narrower terms: mesomorphic] [1913 Webster + WordNet 1.5]WordNet (r) 3.0 (2006):
bullnecked adj 1: having a thick short powerful neck