The Collaborative International Dictionary of English v.0.48:

Stage manager \Stage manager\ (Theat.)
   One in control of the stage during the production of a play.
   He directs the stage hands, property man, etc., has charge of
   all details behind the curtain, except the acting, and has a
   general oversight of the actors. Sometimes he is also the
   stage director.
   [Webster 1913 Suppl.]

WordNet (r) 3.0 (2006):

stage manager
    n 1: someone who supervises the physical aspects in the
         production of a show and who is in charge of the stage when
         the show is being performed [syn: stage manager,
         stager]

Moby Thesaurus II by Grady Ward, 1.0:

30 Moby Thesaurus words for "stage manager":
   MC, auteur, ballyhoo man, barker, callboy, costume designer,
   costumer, costumier, director, emcee, equestrian director,
   exhibitor, impresario, makeup man, master of ceremonies,
   playreader, producer, prompter, ringmaster, scenewright,
   set designer, showman, spieler, stage director, theater man,
   theatrician, ticket collector, usher, usherer, usherette