The Collaborative International Dictionary of English v.0.48:

Impetuosity \Im*pet`u*os"i*ty\, n. [Cf. F. imp['e]tuosit['e].]
   1. The condition or quality of being impetuous; fury;
      violence.
      [1913 Webster]

   2. Vehemence, or furiousnes of temper. --Shak.
      [1913 Webster]

WordNet (r) 3.0 (2006):

impetuosity
    n 1: rash impulsiveness [syn: impetuousness, impetuosity]