Source : Webster's Revised Unabridged Dictionary (1913)

Ennui \En`nui"\, n. [F., fr. L. in odio in hatred. See {Annoy}.]
   A feeling of weariness and disgust; dullness and languor of
   spirits, arising from satiety or want of interest; tedium.
   --T. Gray.

Source : WordNet®

ennui
     n : the feeling of being bored by something tedious [syn: {boredom},
          {tedium}]