What does abutment mean?
The definition of abutment
A*but”ment, n.
1 State of abutting.
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.