[1] : The Collaborative International Dictionary of English v.0.48

shooter \shoot"er\, n.
   1. one who shoots, as an archer or a gunner.
      1913 webster

   2. that which shoots. specifically:
      a a firearm; as, a five-shooter. colloq. u.s.
      b a shooting star. r.
          1913 webster

[2] : WordNet (r) 2.0

shooter
     n 1: a large marble used for shooting in the game of marbles
          syn: taw
     2: a person who shoots usually with respect to their ability
        to shoot; "he is a crack shot"; "a poor shooter" syn: shot
     3: a gambler who throws dice in the game of craps syn: crap-shooter
     4: sports a player who drives or kicks a ball at the goal or
        a basketball player who shoots at the basket
     5: a professional killer who uses a gun syn: gunman, gunslinger,
         hired gun, gun, gun for hire, triggerman, hit
        man, hitman, torpedo
see also:
taw shot crap-shooter gunman gunslinger hired gun 
gun gun for hire triggerman hit man hitman 
torpedo 

Shooter >> S Words
Shooter, definition of term: Shooter
shooter_pag1.html

Trouble Shooter >> T Words
Trouble Shooter, definition of term: Trouble Shooter
trouble+shooter_pag1.html

Square Shooter >> S Words
Square Shooter, definition of term: Square Shooter
square+shooter_pag1.html