The Collaborative International Dictionary of English v.0.48:

Maturation \Mat`u*ra"tion\, n. [L. maturatio a hastening: cf. F.
   maturation.]
   The process of bringing, or of coming, to maturity; hence,
   specifically, the process of suppurating perfectly; the
   formation of pus or matter.
   [1913 Webster]

WordNet (r) 3.0 (2006):

maturation
    n 1: coming to full development; becoming mature [syn:
         maturation, ripening, maturement]
    2: (biology) the process of an individual organism growing
       organically; a purely biological unfolding of events involved
       in an organism changing gradually from a simple to a more
       complex level; "he proposed an indicator of osseous
       development in children" [syn: growth, growing,
       maturation, development, ontogeny, ontogenesis] [ant:
       nondevelopment]
    3: (medicine) the formation of morbific matter in an abscess or
       a vesicle and the discharge of pus [syn: festering,
       suppuration, maturation]

Moby Thesaurus II by Grady Ward, 1.0:

67 Moby Thesaurus words for "maturation":
   accomplishment, advance, advancement, aging, amplification,
   beautification, blossoming, budding, burgeoning, close, completing,
   completion, conclusion, culmination, development,
   developmental change, elaboration, embellishment, end, ending,
   enlargement, evolution, evolutionary change, evolvement, evolving,
   excrescence, expansion, explication, finish, finishing, flowering,
   full development, furtherance, gemmation, germination,
   gradual change, growth, maturescence, maturity, mellowing,
   natural development, natural growth, nonviolent change, outgrowth,
   overgrowth, perfection, procreation, progress, progression,
   pullulation, refinement, reproduction, ripeness, ripening, rise,
   rounding off, rounding out, seasoning, senescence, sprouting,
   tempering, termination, terminus, topping off, upgrowth,
   vegetation, windup