Source : Webster's Revised Unabridged Dictionary (1913)

Belles-lettres \Belles-let"tres\, n. pl. [F.]
   Polite or elegant literature; the humanities; -- used
   somewhat vaguely for literary works in which imagination and
   taste are predominant.

Source : WordNet®

belles-lettres
     n : creative writing valued for esthetic content [syn: {belles
         lettres}]