Source : Webster's Revised Unabridged Dictionary (1913)

Alacrity \A*lac"ri*ty\, n. [L. alacritas, fr. alacer lively,
   eager, prob. akin to Gr. ? to drive, Goth. aljan zeal.]
   A cheerful readiness, willingness, or promptitude; joyous
   activity; briskness; sprightliness; as, the soldiers advanced
   with alacrity to meet the enemy.

         I have not that alacrity of spirit, Nor cheer of mind
         that I was wont to have.                 --Shak.

Source : WordNet®

alacrity
     n : liveliness and eagerness; "he accepted with alacrity" [syn:
         {briskness}]