The Collaborative International Dictionary of English v.0.48:

Leverage \Lev"er*age\ (l[e^]v"[~e]r*[asl]j or
   l[=e]"v[~e]r*[asl]j), n.
   The action of a lever; mechanical advantage gained by the
   lever.
   [1913 Webster]

   Leverage of a couple (Mech.), the perpendicular distance
      between the lines of action of two forces which act in
      parallel and opposite directions.

   Leverage of a force, the perpendicular distance from the
      line in which a force acts upon a body to a point about
      which the body may be supposed to turn.
      [1913 Webster]

WordNet (r) 3.0 (2006):

leverage
    n 1: the mechanical advantage gained by being in a position to
         use a lever [syn: leverage, purchase]
    2: strategic advantage; power to act effectively; "relatively
       small groups can sometimes exert immense political leverage"
    3: investing with borrowed money as a way to amplify potential
       gains (at the risk of greater losses) [syn: leverage,
       leveraging]
    v 1: supplement with leverage; "leverage the money that is
         already available"
    2: provide with leverage; "We need to leverage this company"