(1):
(n.) The solid part of a pier or wall, etc., which receives the thrust or lateral pressure of an arch, vault, or strut.
(2):
(n.) 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.
(3):
(n.) That on or against which a body abuts or presses
(4):
(n.) State of abutting.
(5):
(n.) In breech-loading firearms, the block behind the barrel which receives the pressure due to recoil.