The Collaborative International Dictionary of English v.0.48:

Batman \Bat"man\ (b[a^]t"m[a^]n), n. [Turk. ba[.t]man.]
   A weight used in the East, varying according to the locality;
   in Turkey, the greater batman is about 157 pounds, the lesser
   only a fourth of this; at Aleppo and Smyrna, the batman is 17
   pounds. --Simmonds.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Batman \Bat"man\ (b[add]"man or b[a^]t"man), n.; pl. Batmen
   (b[a^]t"men). [F. b[^a]t packsaddle + E. man. Cf.
   Bathorse.]
   A man who has charge of a bathorse and his load. --Macaulay.
   [1913 Webster]

WordNet (r) 3.0 (2006):

batman
    n 1: an orderly assigned to serve a British military officer

Moby Thesaurus II by Grady Ward, 1.0:

31 Moby Thesaurus words for "batman":
   Ganymede, Hebe, airline hostess, airline stewardess, attendant,
   bellboy, bellhop, bellman, bootblack, boots, cabin boy, caddie,
   chore boy, copyboy, cupbearer, errand boy, errand girl, footboy,
   gofer, hostess, office boy, office girl, orderly, page, squire,
   steward, stewardess, tender, trainbearer, usher, yeoman