The Collaborative International Dictionary of English v.0.48:

Exhibitor \Ex*hib"it*or\, n. [Cf. L. exhibitor a giver.]
   One who exhibits.
   [1913 Webster]

WordNet (r) 3.0 (2006):

exhibitor
    n 1: someone who organizes an exhibit for others to see [syn:
         exhibitor, exhibitioner, shower]