Sniper

Noun

 * 1) A person who carries the professional title of sniper
 * 2) A person using long-range small arms for precise attacks from a concealed position.
 * 3) Any attacker using a non-contact weapon against a specific target from a concealed position.

Thesaurus
archer, artilleryman, bersagliere, bowman, cannoneer, carabineer, chasseur, crack shot, dead shot, deadeye, dogface, doughfoot, expert rifleman, foot soldier, footslogger, fusileer, good shot, grenadier, grunt, gun, gunman, gunner, hunter, infantryman, light infantryman, marksman, markswoman, musketeer, paddlefoot, rifle, rifleman, sharpshooter, shooter, shot, targetshooter, toxophilite, trapshooter