The Collaborative International Dictionary of English v.0.48:

Abutment \A*but"ment\ ([.a]*b[u^]t"ment), n.
   1. State of abutting.
      [1913 Webster]

   2. That on or against which a body abuts or presses; as
      (a) (Arch.) The solid part of a pier or wall, etc., which
          receives the thrust or lateral pressure of an arch,
          vault, or strut. --Gwilt.
      (b) (Mech.) A fixed point or surface from which resistance
          or reaction is obtained, as the cylinder head of a
          steam engine, the fulcrum of a lever, etc.
      (c) In breech-loading firearms, the block behind the
          barrel which receives the pressure due to recoil.
          [1913 Webster]

WordNet (r) 3.0 (2006):

abutment
    n 1: point of contact between two objects or parts
    2: a masonry support that touches and directly receives thrust
       or pressure of an arch or bridge