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