2. A perforated block (usually a small piece of metal),
provided with an internal or female screw thread, used on
a bolt, or screw, for tightening or holding something, or
for transmitting motion. See Illust. of lst {Bolt}.
3. The tumbler of a gunlock. --Knight.
4. (Naut.) A projection on each side of the shank of an
anchor, to secure the stock in place.
{Check nut}, {Jam nut}, {Lock nut}, a nut which is screwed up
tightly against another nut on the same bolt or screw, in
order to prevent accidental unscrewing of the first nut.
{Nut coal}, screened coal of a size smaller than stove coal
and larger than pea coal; -- called also {chestnut coal}.
{Nut crab} (Zo["o]l.), any leucosoid crab of the genus
{Ebalia} as, {Ebalia tuberosa} of Europe.
{Nut grass} (Bot.), a plant of the Sedge family ({Cyperus
rotundus}, var. Hydra), which has slender rootstocks
bearing small, nutlike tubers, by which the plant
multiplies exceedingly, especially in cotton fields.
{Nut lock}, a device, as a metal plate bent up at the
corners, to prevent a nut from becoming unscrewed, as by
jarring.
{Anchor buoy}, a buoy attached to, or marking the position
of, an anchor.
{Bell buoy}, a large buoy on which a bell is mounted, to be
rung by the motion of the waves.
{Breeches buoy}. See under {Breeches}.
{Cable buoy}, an empty cask employed to buoy up the cable in
rocky anchorage.
{Can buoy}, a hollow buoy made of sheet or boiler iron,
usually conical or pear-shaped.
{Life buoy}, a float intended to support persons who have
fallen into the water, until a boat can be dispatched to
save them.
{Nut} or {Nun buoy}, a buoy large in the middle, and tapering
nearly to a point at each end.
{To stream the buoy}, to let the anchor buoy fall by the
ship's side into the water, before letting go the anchor.
{Whistling buoy}, a buoy fitted with a whistle that is blown
by the action of the waves.