WordNet (r) 3.0 (2006):

adulthood
    n 1: the period of time in your life after your physical growth
         has stopped and you are fully developed [syn: adulthood,
         maturity]
    2: the state (and responsibilities) of a person who has attained
       maturity

Moby Thesaurus II by Grady Ward, 1.0:

25 Moby Thesaurus words for "adulthood":
   adultness, age of consent, driving age, flower of age, full age,
   full bloom, full growth, fullgrownness, grown-upness, legal age,
   legalis homo, majority, manhood, manlihood, mature age, maturity,
   prime, prime of life, ripe age, riper years, toga virilis,
   virility, womanhood, womanlihood, years of discretion