To look or observe attentively or carefully; be closely observant: watching for trail markers. To look and wait expectantly or in anticipation: watch for an opportunity. To act as a spectator; look on: stood by the road and watched. To stay awake at night while serving as a guard, sentinel, or watcher. To stay alert as a devotional or religious exercise; keep vigil. To look at steadily; observe carefully or continuously: watch a parade. To keep a watchful eye on; guard: watched the prisoner all day. To observe the course of mentally; keep up on or informed about: watch the price of gold. To tend (a flock, for example). See Synonyms at tend2. The act or process of keeping awake or mentally alert, especially for the purpose of guarding. The act of observing closely or the condition of being closely observed; surveillance. A period of close observation, often in order to discover something: a watch during the child's illness. A person or group of people serving, especially at night, to guard or protect. The post or period of duty of a guard, sentinel, or watcher. Any of the periods into which the night is divided; a part of the night. Nautical 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. Nautical The members of a ship's crew on duty during a specific watch. Nautical A chronometer on a ship. A period of wakefulness, especially one observed as a religious vigil. A funeral wake. A small portable timepiece, especially one worn on the wrist or carried in the pocket. A flock of nightingales. See Synonyms at flock1. watch out To be careful or on the alert; take care. watch over To be in charge of; superintend. watch it To be careful: had to watch it when I stepped onto the ice.