The Collaborative International Dictionary of English v.0.48:

Shortstop \Short"stop`\, n. (Baseball)
   The player stationed in the field bewtween the second and
   third bases.
   [1913 Webster]

WordNet (r) 3.0 (2006):

shortstop
    n 1: (baseball) the person who plays the shortstop position
    2: the fielding position of the player on a baseball team who is
       stationed between second and third base [syn: shortstop,
       short]

Moby Thesaurus II by Grady Ward, 1.0:

42 Moby Thesaurus words for "shortstop":
   amateur athlete, archer, athlete, ballplayer, baseballer, baseman,
   batter, battery, blocking back, bowman, catcher, center, coach,
   competitor, cricketer, defensive lineman, end, footballer,
   games-player, gamester, guard, infielder, jock, jumper, lineman,
   offensive lineman, outfield, outfielder, player, poloist,
   professional athlete, pugilist, quarterback, racer, skater, sport,
   sportsman, tackle, tailback, toxophilite, wingback, wrestler