picket

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

• noun A pointed stake often driven into the ground to support a fence, secure a tent, tether animals, mark points in surveying, or, when pointed at the top, serve as a defense.
• noun A detachment of one or more troops, ships, or aircraft held in readiness or advanced to warn of an enemy's approach.
• noun A person or group of persons stationed outside a place of employment, usually during a strike, to express grievance or protest and discourage entry by nonstriking employees or customers.
• noun A person or group of persons present outside a building to protest.
• intransitive verb To enclose, secure, tether, mark out, or fortify with pickets.
• intransitive verb To post as a picket.
• intransitive verb To guard with a picket.
• intransitive verb To post a picket or pickets during a strike or demonstration.
• intransitive verb To act or serve as a picket.

from The Century Dictionary.

• To place a picket or guard (see picket, n., 3) near a shop or mill, during a strike, to prevent men who do not belong to the striking organization or body from obtaining work in the shop, or to prevent the employers from securing such laborers.
• noun The tern or sea-swallow. Also pickie.
• To fortify with pickets or pointed stakes; also, to inclose or fence with narrow pointed boards or pales.
• To fasten to a picket or stake, as a horse.
• To torture by compelling to stand with one foot on a pointed stake.
• To place or post as a guard of observation.
• To make into pickets.
• noun A pointed post, stake, or bar, usually of wood.
• noun Milit.: A guard posted in front of an army to give notice of the approach of the enemy: called-an outlying picket.
• noun A detachment of troops in a camp kept fully equipped and ready for immediate service in case of an alarm or the approach of an enemy: called an inlying picket.
• noun A small detachment of men sent out from a camp or garrison to bring in such of the soldiers as have exceeded their leave. See guard, post, etc.
• noun A body of men belonging to a trades-union sent to watch and annoy men working in a shop not belonging to the union, or against which a strike is in progress.
• noun A game at cards. See piquet.
• noun A punishment which consists in making the offender stand with one foot on a pointed stake.
• noun An elongated projectile pointed in front.

from the GNU version of the Collaborative International Dictionary of English.

• transitive verb To fortify with pointed stakes.
• transitive verb To inclose or fence with pickets or pales.
• transitive verb To tether to, or as to, a picket.
• transitive verb To guard, as a camp or road, by an outlying picket.
• transitive verb obsolete To torture by compelling to stand with one foot on a pointed stake.
• noun A stake sharpened or pointed, especially one used in fortification and encampments, to mark bounds and angles; or one used for tethering horses.
• noun A pointed pale, used in marking fences.
• noun (Mil.) A detached body of troops serving to guard an army from surprise, and to oppose reconnoitering parties of the enemy; -- called also outlying picket.
• noun Cant By extension, men appointed by a trades union, or other labor organization, to intercept outsiders, and prevent them from working for employers with whom the organization is at variance.
• noun A military punishment, formerly resorted to, in which the offender was forced to stand with one foot on a pointed stake.
• noun A game at cards. See Piquet.
• noun (Mil.) a detachment of troops held in camp or quarters, detailed to march if called upon.
• noun a fence made of pickets. See def. 2, above.
• noun (Mil.) a guard of horse and foot, always in readiness in case of alarm.
• noun (Mil.) A rope to which horses are secured when groomed.
• noun an iron pin for picketing horses.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun A stake driven into the ground.
• noun historical A type of punishment by which an offender had to rest his or her entire body weight on the top of a small stake.
• noun A tool in mountaineering that is driven into the snow and used as an anchor or to arrest falls.
• noun military Soldiers or troops placed on a line forward of a position to warn against an enemy advance. It can also refer to any unit (for example, an aircraft or ship) performing a similar function.
• noun A sentry. Can be used figuratively.
• noun A protester positioned outside an office, workplace etc. during a strike (usually in plural); also the protest itself.
• verb intransitive To protest, organized by a labour union, typically in front of the location of employment.
• verb transitive To enclose or fortify with pickets or pointed stakes.