The Collaborative International Dictionary of English v.0.48:

Disembarkation \Dis*em`bar*ka"tion\, n.
   The act of disembarking.
   [1913 Webster]

WordNet (r) 3.0 (2006):

disembarkation
    n 1: the act of passengers and crew getting off of a ship or
         aircraft [syn: debarkation, disembarkation,
         disembarkment] [ant: boarding, embarkation,
         embarkment]