The Collaborative International Dictionary of English v.0.48:
hashmark \hash"mark`\ n. (Mil.) an insignia worn on the uniform to indicate years of service. Syn: service stripe, hash mark. [WordNet 1.5]WordNet (r) 3.0 (2006):
hashmark n 1: an insignia worn to indicate years of service [syn: service stripe, hashmark, hash mark]