The Collaborative International Dictionary of English v.0.48:

Antimason \An`ti*ma"son\ ([a^]n`t[i^]*m[=a]"s'n), n.
   One opposed to Freemasonry. -- An`ti*ma*son"ic
   ([a^]n`t[i^]*m[.a]*s[o^]n"[i^]k), a.
   [1913 Webster]