The Collaborative International Dictionary of English v.0.48:

Gunner \Gun"ner\, n.
   1. One who works a gun or cannon, whether on land, sea, or in
      the air; a cannoneer.
      [1913 Webster]

   2. A warrant officer in the navy having charge of the
      ordnance on a vessel.
      [1913 Webster]

   3. (Zool.)
      (a) The great northern diver or loon. See Loon.
      (b) The sea bream. [Prov. Eng. or Irish]
          [1913 Webster]

   Gunner's daughter, the gun to which men or boys were lashed
      for punishment. [Sailor's slang] --W. C. Russell.

   tail gunner (Mil.) A member of the crew of a bomber
      airplane who operates the defensive gun at the rear of the
      airplane.
      [1913 Webster +PJC]

WordNet (r) 3.0 (2006):

gunner
    n 1: a serviceman in the artillery [syn: artilleryman,
         cannoneer, gunner, machine gunner]