The Collaborative International Dictionary of English v.0.48:

Transitional \Tran*si"tion*al\, a.
   Of or pertaining to transition; involving or denoting
   transition; as, transitional changes; transitional stage.
   [1913 Webster]

WordNet (r) 3.0 (2006):

transitional
    adj 1: of or relating to or characterized by transition;
           "adolescence is a transitional stage between childhood
           and adulthood"

Moby Thesaurus II by Grady Ward, 1.0:

26 Moby Thesaurus words for "transitional":
   active, altering, changing, convertible, developing, driving,
   evolving, impelling, in motion, mobile, modifiable, motile,
   motivational, motive, motor, moving, propellant, propelling,
   resolvable, shifting, stirring, transformable, transitive,
   transitory, transmutable, traveling