watch 
(wŏch)
(wŏch)v. watched, watch·ing, watch·es
v.intr.
1. To look or observe attentively or carefully; be closely observant: watching for trail markers.
2. To look and wait expectantly or in anticipation: watch for an opportunity.
3. To act as a spectator; look on: stood by the road and watched.
4. To stay awake at night while serving as a guard, sentinel, or watcher.
5. To stay alert as a devotional or religious exercise; keep vigil.
v.tr.
1. To look at steadily; observe carefully or continuously: watch a parade.
2. To guard, keep surveillance on, or spy on: watched the prisoner all day; watched the house to see who came and went.
3. To observe the course of mentally; keep up on or informed about: watch the price of gold.
4. To pay close attention to or be careful about, especially with regard to propriety: watched his manners.
5. To tend or take care of (children or a flock of sheep, for example). See Synonyms at tend2.
n.
Phrasal Verbs: 1. The act or process of keeping awake or mentally alert, especially for the purpose of guarding.
2.
a. The act of observing closely or the condition of being closely observed; surveillance.
b. A period of close observation, often in order to discover something: a watch during the child's illness.
3. A person or group of people serving, especially at night, to guard or protect.
4. The post or period of duty of a guard, sentinel, or watcher.
5. Any of the periods into which the night is divided; a part of the night.
6. Nautical
a. Any of the periods of time, usually four hours, into which the day aboard ship is divided and during which a part of the crew is assigned to duty.
b. The members of a ship's crew on duty during a specific watch.
c. A chronometer on a ship.
7.
a. A period of wakefulness, especially one observed as a religious vigil.
b. A funeral wake.
8. A small portable timepiece, especially one worn on the wrist or carried in the pocket.
9. A flock of nightingales.
watch out
To be careful or on the alert; take care.
watch over
Idioms: To be in charge of; superintend.
watch it
To be careful: had to watch it when I stepped onto the ice.
watch (one's) step
1. To act or proceed with care and caution.
2. To behave as is demanded, required, or appropriate.
[Middle English wacchen, from Old English wæccan, to watch, be awake; see weg- in the Appendix of Indo-European roots.]