2. A ring of metal, leather, or other material, or a perforated plate,
used for various purposes, as around a bolt or screw to form a seat for
the head or nut, or around a wagon axle to prevent endwise motion of
the hub of the wheel and relieve friction, or in a joint to form a
packing, etc.
3. (Plumbing) A fitting, usually having a plug, applied to a cistern,
tub, sink, or the like, and forming the outlet opening.