The Collaborative International Dictionary of English v.0.48:

Claymore \Clay"more`\ (kl[=a]"m[=o]r`), n. [Gael. claidheamhmor
   a broadsword; Gael. claidheamh sword + mor great, large. Cf.
   Glaymore.]
   A large two-handed sword used formerly by the Scottish
   Highlanders.
   [1913 Webster]

WordNet (r) 3.0 (2006):

claymore
    n 1: a large double-edged broadsword; formerly used by Scottish
         Highlanders
    2: an antipersonnel land mine whose blast is aimed at the
       oncoming enemy [syn: claymore mine, claymore]