Source : Webster's Revised Unabridged Dictionary (1913)

Ametabolic \A*met`a*bol"ic\, Ametabolous \Am`e*tab"o*lous\, a.
   (Zo["o]l.)
   Not undergoing any metamorphosis; as, ametabolic insects.

Source : WordNet®

ametabolic
     adj 1: undergoing slight or no metamorphosis [syn: {ametabolous}]
            [ant: {metabolic}]
     2: undergoing no (or only slight) metamorphosis