picket

noun

1.
a person employed to keep watch for some anticipated event
lookout scout sentinel sentry spotter watch
2.
a detachment of troops guarding an army from surprise attack
3.
a protester posted by a labor organization outside a place of work
Derived from:
picket
4.
a vehicle performing sentinel duty
5.
a wooden strip forming part of a fence
pale
Derived from:
picket
6.
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
piquet