The Collaborative International Dictionary of English v.0.48:

Impatience \Im*pa"tience\n. [OE. impacience, F. impatience, fr.
   L. impatientia.]
   The quality of being impatient; lack of endurance of pain,
   suffering, opposition, or delay; eagerness for change, or for
   something expected; restlessness; chafing of spirit;
   fretfulness; passion; as, the impatience of a child or an
   invalid.
   [1913 Webster]

         I then, . . .
         Out of my grief and my impatience,
         Answered neglectingly.                   --Shak.
   [1913 Webster]

         With huge impatience he inly swelt
         More for great sorrow that he could not pass,
         Than for the burning torment which he felt. --Spenser.
   [1913 Webster]

WordNet (r) 3.0 (2006):

impatience
    n 1: a lack of patience; irritation with anything that causes
         delay [syn: restlessness, impatience]
    2: a restless desire for change and excitement
    3: a dislike of anything that causes delay [ant: forbearance,
       longanimity, patience]

Moby Thesaurus II by Grady Ward, 1.0:

40 Moby Thesaurus words for "impatience":
   alacrity, animation, anxiety, anxiousness, appetite, avidity,
   avidness, breathless impatience, cheerful readiness, eagerness,
   elan, forwardness, gust, gusto, haste, hastiness, impetuosity,
   impetuousness, impulsiveness, keen desire, keenness, life,
   liveliness, overhastiness, precipitance, precipitancy,
   precipitateness, precipitation, promptness, quickness, rashness,
   readiness, recklessness, spirit, suddenness, verve, vitality,
   vivacity, zest, zestfulness