Ennui, the state or condition of one that is bored. Many fanciful derivations of the word have been affirmed, but so high an authority as Father Jape says that it comes from a very obvious source -- the first words of the ancient Latin hymn _Te Deum Laudamus_. In this apparently natural derivation there is something that saddens.

the feeling of being bored by something tedious

Irksomeness; wearisomeness; tediousness.

Principle of training which states we must vary training methods to prevent boredom and over use injuries.

dullness owing to length or slowness