noun

1. the act or fact of keeping awake, esp. of keeping awake and alert, in order to look after, protect, or guard
2. 1. any of the several periods into which the night was divided in ancient times
   2. a part of the night the still watches of the night
3. 1. close observation for a time, in order to see or find out something
   2. the act or process of vigilant, careful guarding to keep watch over a house
4. a person or group on duty, esp. at night, to protect or guard; lookout or guard
5. 1. the period of duty of a guard
   2. the post of a guard
6. a small timepiece designed to be carried in the pocket or worn on the wrist, as a pendant, etc.
7. Obsolete
   1. a vigil; wake
   2. vigilance
8. Obsolete a candle marked off into sections, used for keeping time
9. Obsolete a watchman's cry
10. Naut.
    1. any of the periods of duty (five of four hours, and two of two hours) into which the day is divided on shipboard, so that the work is shared among alternating shifts of the crew
    2. the part of the crew on duty during any such period
    3. a ship's chronometer

Etymology: ME wacche < OE wæcce < base of wacian: see wake

intransitive verb

1. to stay awake, esp. at night, so as to pray and meditate
2. to stay awake and alert at night; care for or guard something at night
3. to be on the alert; be on the lookout
4. to look or observe, esp. attentively
5. to be looking or waiting attentively: with for to watch for one's chance

transitive verb

1. to guard
2. to keep looking at; observe carefully and constantly
3. to view mentally; keep informed about
4. to be on the alert for; wait for and look for to watch one's chance
5. to keep watch over or tend (a flock, a baby, etc.)