Source : Webster's Revised Unabridged Dictionary (1913)

Pronoun \Pro"noun\, n. [Pref. pro- + noun: cf. F. pronom, L.
   pronomen. See {Noun}.] (Gram.)
   A word used instead of a noun or name, to avoid the
   repetition of it. The personal pronouns in English are I,
   thou or you, he, she, it, we, ye, and they.

Source : WordNet®

pronoun
     n : a function word that is used in place of a noun or noun
         phrase