Precocious

precocious
    adj 1: characterized by or characteristic of exceptionally early
           development or maturity (especially in mental aptitude);
           "a precocious child"; "a precocious achievement" [ant:
           {retarded}]
    2: appearing or developing early; "precocious flowers appear
       before the leaves as in some species of magnolias"
    

Precocious \Pre*co"cious\, a. [L. praecox, -ocis, and
   praecoquus, fr. praecoquere to cook or ripen beforehand; prae
   before + coquere to cook. See 3d {Cook}, and cf. {Apricot}.]
   1. Ripe or mature before the proper or natural time; early or
      prematurely ripe or developed; as, precocious trees. [R.]
      --Sir T. Browne.
      [1913 Webster]

   2. Developed more than is natural or usual at a given age;
      exceeding what is to be expected of one's years; too
      forward; -- used especially of mental forwardness; as, a
      precocious child; precocious talents.
      [1913 Webster]
    

36 Moby Thesaurus words for "precocious":
      a bit previous, advanced, ahead, bright, developed, early,
      far ahead, forward, gifted, half-baked, half-cocked, hasty,
      ill-considered, impulsive, intelligent, mature, not firm,
      overhasty, oversoon, precipitate, premature, previous, quick,
      rushed, smart, soon, too early, too soon, uncrystallized, unjelled,
      unmatured, unmeditated, unpremeditated, unprepared, unripe,
      untimely