watch

noun

1.
a small portable timepiece
ticker
2.
a period of time (4 or 2 hours) during which some of a ship's crew are on duty
3.
a purposeful surveillance to guard or observe
vigil
Derived from:
watch
4.
the period during which someone (especially a guard) is on duty
5.
a person employed to keep watch for some anticipated event
lookout picket scout sentinel sentry spotter
Derived from:
watch
6.
the rite of staying awake for devotional purposes (especially on the eve of a religious festival)
vigil