The Collaborative International Dictionary of English v.0.48:

Stager \Sta"ger\ (st[=a]"j[~e]r), n.
   1. A player. [R.] --B. Jonson.
      [1913 Webster]

   2. One who has long acted on the stage of life; a
      practitioner; a person of experience, or of skill derived
      from long experience. "You will find most of the old
      stagers still stationary there." --Sir W. Scott.
      [1913 Webster]

   3. A horse used in drawing a stage. [Colloq.]
      [1913 Webster]

WordNet (r) 3.0 (2006):

stager
    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]
    2: an experienced person who has been through many battles;
       someone who has given long service [syn: veteran, old-
       timer, oldtimer, old hand, warhorse, old stager,
       stager]