- a stake or slat, usually pointed, used as an upright in a fence, a hitching post for animals, a marker, etc.
- a group of soldiers or a single soldier stationed, usually at an outpost, to guard a body of troops from surprise attack
- a ship or airplane that patrols a defense perimeter
- a person, as a member of a labor union on strike, stationed outside a factory, store, or public building, often carrying a sign, to demonstrate opposition to certain views or practices, keep strikebreakers from entering, or dissuade people from buying
Fr piquet < piquer, to pierce < pic, pike
to serve as a picket (sense )