The Collaborative International Dictionary of English v.0.48:

Mastotermes \Mastotermes\ prop. n.
   A primitive genus of termites, mostly extinct; sometimes
   considered the most primitive isopterans.

   Syn: genus Mastotermes.
        [WordNet 1.5]

WordNet (r) 3.0 (2006):

Mastotermes
    n 1: primitive genus of termites; mostly extinct; sometimes
         considered the most primitive Isoptera [syn: Mastotermes,
         genus Mastotermes]