The Collaborative International Dictionary of English v.0.48:

Ecdysis \Ec"dy*sis\, n.; pl. Ecdyses. [NL., fr. Gr. 'e`kdysis
   a getting out, fr. 'ekdy`ein, to put off; 'ek out + dy`ein to
   enter.] (Biol.)
   The act of shedding, or casting off, an outer cuticular
   layer, as in the case of serpents, lobsters, etc.; a coming
   out; as, the ecdysis of the pupa from its shell; exuviation.
   [1913 Webster]

WordNet (r) 3.0 (2006):

ecdysis
    n 1: periodic shedding of the cuticle in arthropods or the outer
         skin in reptiles [syn: molt, molting, moult,
         moulting, ecdysis]