spur

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A short spike or spiked wheel that attaches to the heel of a rider's boot and is used to urge a horse forward.
• noun An incentive.
• noun A spurlike attachment or projection, as.
• noun A spinelike process on the leg of some birds.
• noun A climbing iron; a crampon.
• noun A gaff attached to the leg of a gamecock.
• noun A short or stunted branch of a tree.
• noun A bony outgrowth or protuberance.
• noun A lateral ridge projecting from a mountain or mountain range.
• noun An oblique reinforcing prop or stay of timber or masonry.
• noun Botany A tubular or saclike extension of the corolla or calyx of a flower, as in a columbine or larkspur.
• noun An ergot growing on rye.
• noun A spur track.
• intransitive verb To urge (a horse) on by the use of spurs.
• intransitive verb To incite or stimulate.
• intransitive verb To ride quickly by spurring a horse.

from The Century Dictionary.

• To prick or rasp with the point or rowel of a spur.
• Figuratively, to urge or incite.
• To hasten.
• To fasten spurs to, as a horseman's boot, or a solleret.
• To furnish with spurs, as a rider: as, booted and spurred; to furnish with a spur or gaff, as a game-cock.
• To prop; support.
• To prick one's horse with the spur; ride in haste.
• Figuratively, to press forward.
• noun The ridge in the interior of a bifurcating tube between the two branches given off from it.
• noun In horticulture, a twig or short branch that bears flowers and fruit, in distinction from one that continues to elongate in woody growth.
• noun A side-track running out from a main railway line and forming part of a Y.
• noun A pointed instrument worn on the heel by a horseman to goad the horse.
• noun Anything which goads, impels, or urges to action; incitement; instigation; incentive; stimulus: used in this sense in the phrase on or upon the spur of the moment—that is, on a momentary impulse; suddenly; hastily; impromptu.
• noun Some projecting thing more or less closely resembling a horseman's spur in form or position.
• noun plural Short small twigs projecting a few inches from the trunk.
• noun A snag; a spine; specifically, in herpetology:
• noun An anal spur.
• noun A calcar of some frogs.
• noun In entomology, a spine or stiff bristle on the leg.
• noun In ornithology: A horny modification of the integument of a bird's foot, forming an outgrowth of the nature of a claw, usually sharp-pointed and supported on a bony core, and used as a weapon of offense and defense; a calcar. Such a spur differs from a clan mainly in not ending a digit, but being an offset from the side of the metatarsus; it is also characteristic; of though not confined to the male, and is therefore a secondary sexual character. It is familiar as occurring on the shank of the domestic cock and other gallinaceous birds, and is sometimes double or treble, as in Pavo bicalcaratus and in the genera Galloperdix, Ithaginis, and Polyplectron. See cuts under calcarate, Galloperdix, Ithaginis, pea-fowl, Polyplectron, Rasores, and tarsometatarsus. A similar horny outgrowth on the pinion-bone of the wing in various birds, resembling a claw, but differing in being a lateral offset not terminating a digit. It occurs in certain geese, plovers, pigeons, and jacanas, and is double in the screamer. See cuts under jacana, Palamedea, and spur-winged.
• noun In sporting, a gaff, or sharp piercing or cutting instrument fastened upon the natural spur of a game-cock In the pit.
• noun In mammalogy, the calcarof some bats.
• noun In physical geography, a ridge or line of elevation subordinate to the main body or crest of a mountainrange; one of the lower divisions of a mountain-mass, when this, as is frequently the case, is divided by valleys or gorges. See mountain-chain.
• noun A climbing-iron used in mounting telegraph-poles and the like.
• noun (J) In carpentry, a brace connecting or strengthening a post and some other part, as a rafter or cross-beam.
• noun In architecture, any offset from a wall, etc., as a buttress; specifically, the claw or griffe projecting from the toru sat each of the angles of the base of early Pointed medieval columns.
• noun In botany, a calcar; a slender hollow projection from some part of a flower, as from the calyx of columbine and larkspur and the corolla of violets. It is usually nectariferous, being the nectary (nectarium) of Linnæus. The term is also rarely applied to a solid spur-like process. See also cuts under nectary, columbine, and Delphinium.
• noun In fortification, a wall that crosses a part of the rampart and joins it to an anterior work; also, a tower or blockhouse placed in the outworks before the port
• noun In ship-building;
• noun A shore or piece of timber extending from the bilgeways, and fayed and bolted to the bottom of the ship on the stocks.
• noun A curved piece of timber serving as a half beam to support the deck where a whole beam cannot be placed.
• noun A heavy timber extended from a pier or wharf against the side of a ship to prevent the ship from striking against the pier.
• noun In hydraul, engin., awing-dam, or projection built out from a river-bank to deflect the current.