Source : Webster's Revised Unabridged Dictionary (1913)

Postfix \Post"fix\, n.; pl. {Postfixes}. [Pref. post- + -fix, as
   in prefix: cf. F. postfixe.] (Gram.)
   A letter, syllable, or word, added to the end of another
   word; a suffix. --Parkhurst.

Postfix \Post*fix"\, v. t.
   To annex; specifically (Gram.), to add or annex, as a letter,
   syllable, or word, to the end of another or principal word;
   to suffix. --Parkhurst.

Source : WordNet®

postfix
     n : an affix that is added at the end of the word [syn: {suffix}]