The Collaborative International Dictionary of English v.0.48:

pacifist \pacifist\ n.
   1. A person opposed to violence as a means of settling
      disputes.

   Syn: pacificist, disarmer.
        [WordNet 1.5]

   2. A person whose strong belief in pacifism causes him/her to
      refuse to participate in military activities, especially
      one who refuses to be drafted into the armed forces.
      [PJC] pacifist

The Collaborative International Dictionary of English v.0.48:

pacifist \pacifist\ pacifistic \pacifistic\adj.
   Adhering to pacifism; opposed to war; -- of people.
   [WordNet 1.5]

WordNet (r) 3.0 (2006):

pacifist
    adj 1: opposed to war [syn: pacifist(a), pacifistic,
           dovish]
    n 1: someone opposed to violence as a means of settling disputes
         [syn: pacifist, pacificist, disarmer]