What is the meaning of picket?

noun

• A person employed to keep watch for some anticipated event.
  • synonyms: lookout, lookout man, sentinel, sentry, watch, spotter, scout
• A detachment of troops guarding an army from surprise attack.
• A protester posted by a labor organization outside a place of work.
• A vehicle performing sentinel duty.
• A wooden strip forming part of a fence.
  • synonyms: pale
• A form of military punishment used by the British in the late 17th century in which a soldier was forced to stand on one foot on a pointed stake.
  • synonyms: piquet

verb

• Serve as pickets or post pickets.
  • usage: "picket a business to protest the layoffs"
• Fasten with a picket.
  • usage: "picket the goat"