Source : Webster's Revised Unabridged Dictionary (1913)

Pleasantness \Pleas"ant*ness\, n.
   The state or quality of being pleasant.

Source : WordNet®

pleasantness
     n 1: the feeling caused by agreeable stimuli; one pole of a
          continuum of states of feeling [ant: {unpleasantness}]
     2: the quality of giving pleasure; "he was charmed by the
        sweetness of her manner"; "the pleasantness of a cool
        breeze on a hot summer day" [syn: {sweetness}] [ant: {unpleasantness}]