The Collaborative International Dictionary of English v.0.48:

Dead-eye \Dead"-eye`\ (d[e^]d"[imac]`), n. (Naut.)
   A round, flattish, wooden block, encircled by a rope, or an
   iron band, and pierced with three holes to receive the
   lanyard; -- used to extend the shrouds and stays, and for
   other purposes. Called also deadman's eye. --Totten.
   [1913 Webster]

WordNet (r) 3.0 (2006):

deadeye
    n 1: a dead shot
    2: (nautical) a round hardwood disk with holes and a grooved
       perimeter used to tighten a shroud

Moby Thesaurus II by Grady Ward, 1.0:

52 Moby Thesaurus words for "deadeye":
   Nimrod, air hole, archer, armhole, artilleryman, blowhole, bowman,
   bullet-hole, bunghole, cannoneer, carabineer, crack shot, cringle,
   dead shot, eye, eyelet, gasket, good shot, grommet, guide, gun,
   gunman, gunner, hunter, keyhole, knothole, loop, loophole, manhole,
   marksman, markswoman, mousehole, musketeer, peephole, pigeonhole,
   pinhole, placket, placket hole, porthole, punch-hole, rifleman,
   sharpshooter, shooter, shot, sniper, spiracle, tap, targetshooter,
   toxophilite, trapshooter, vent, venthole