swearer

from WordNet (r) 3.0 (2006)

swearer
    n 1: someone who uses profanity
    2: someone who takes a solemn oath

from The Collaborative International Dictionary of English v.0.48

Swearer \Swear"er\, n.
   1. One who swears; one who calls God to witness for the truth
      of his declaration.
      [1913 Webster]

   2. A profane person; one who uses profane language.
      [1913 Webster]

            Then the liars and swearers are fools. --Shak.
      [1913 Webster]