The Collaborative International Dictionary of English v.0.48:
Headstall \Head"stall`\ (-st[add]l`), n. That part of a bridle or halter which encompasses the head. --Shak. [1913 Webster]WordNet (r) 3.0 (2006):
headstall n 1: the band that is the part of a bridle that fits around a horse's head [syn: headstall, headpiece]