The Collaborative International Dictionary of English v.0.48:

Precipitance \Pre*cip"i*tance\, Precipitancy \Pre*cip"i*tan*cy\,
   n. [From Precipitant.]
   The quality or state of being precipitant, or precipitate;
   headlong hurry; excessive or rash haste in resolving, forming
   an opinion, or executing a purpose; precipitation; as, the
   precipitancy of youth. "Precipitance of judgment." --I.
   Watts.
   [1913 Webster]

WordNet (r) 3.0 (2006):

precipitance
    n 1: the quality of happening with headlong haste or without
         warning [syn: abruptness, precipitateness,
         precipitousness, precipitance, precipitancy,
         suddenness]