The Collaborative International Dictionary of English v.0.48:

Propulsion \Pro*pul"sion\, n. [Cf. F. propulsion. See Propel.]
   1. The act driving forward or away; the act or process of
      propelling; as, steam propulsion.
      [1913 Webster]

   2. An impelling act or movement.
      [1913 Webster]

            God works in all things; all obey
            His first propulsion.                 --Whittier.
      [1913 Webster]

WordNet (r) 3.0 (2006):

propulsion
    n 1: a propelling force
    2: the act of propelling [syn: propulsion, actuation]