The Collaborative International Dictionary of English v.0.48:

Impulsion \Im*pul"sion\, n. [L. impulsio: cf. F. impulsion. See
   Impel.]
   [1913 Webster]
   1. The act of impelling or driving onward, or the state of
      being impelled; the sudden or momentary agency of a body
      in motion on another body; also, the impelling force, or
      impulse. "The impulsion of the air." --Bacon.
      [1913 Webster]

   2. Influence acting unexpectedly or temporarily on the mind;
      sudden motive or influence; impulse. "The impulsion of
      conscience." --Clarendon. "Divine impulsion prompting."
      --Milton.
      [1913 Webster]

WordNet (r) 3.0 (2006):

impulsion
    n 1: a force that moves something along [syn: drift,
         impetus, impulsion]
    2: the act of applying force suddenly; "the impulse knocked him
       over" [syn: impulse, impulsion, impetus]