The Collaborative International Dictionary of English v.0.48:

D'ebut \D['e]`but"\, n. [F. d['e]but, prop., the first cast or
   throw at play, fr. but aim, mark. See Butt an end.]
   A beginning or first attempt; hence, a first appearance
   before the public, as of an actor or public speaker. Debutant

Moby Thesaurus II by Grady Ward, 1.0:

41 Moby Thesaurus words for "debut":
   appear, benefit, bill, come out, coming out, coming-out party,
   curtain raiser, embarkation, embarkment, enter, entertainment,
   exhibit, exhibition, farewell performance, first appearance,
   flesh show, floating, flotation, inaugural address, inauguration,
   induction, initiation, installation, installment, introduction,
   launch, launching, maiden speech, opener, performance, preliminary,
   premiere, presentation, presentment, production, show,
   stage presentation, swan song, theatrical performance, tryout,
   unveiling