WordNet (r) 3.0 (2006):

hash mark
    n 1: an insignia worn to indicate years of service [syn:
         service stripe, hashmark, hash mark]

Moby Thesaurus II by Grady Ward, 1.0:

22 Moby Thesaurus words for "hash mark":
   Hershey bar, aviation badge, badge, bar, chevron, chicken, eagle,
   epaulet, insignia of branch, oak leaf, organization insignia,
   overseas bar, parachute badge, patch, pip, service stripe,
   shoulder patch, shoulder sleeve insignia, spread eagle, star,
   stripe, submarine badge