Source : Webster's Revised Unabridged Dictionary (1913)

Amphoteric \Am`pho*ter"ic\, a. [Gr. ? both.]
   Partly one and partly the other; neither acid nor alkaline;
   neutral. [R.] --Smart.

Source : WordNet®

amphoteric
     adj : having characteristics of both an acid and a base and
           capable of reacting as either [syn: {amphiprotic}]
           [ant: {acidic}, {alkaline}]