1. a person who watches or observes something or someone
2. a person whose job is to guard or keep watch over something

Examples

• The bird watcher sat quietly in the forest with binoculars.
• Police stationed watchers at every entrance to the building.
• She was a keen watcher of political debates on television.
• The night watcher made his rounds every two hours.
• Whale watchers gathered on the pier hoping to see migrating pods.
• The security watcher noticed suspicious activity on the monitors.
• As a longtime watcher of the stock market, he predicted the downturn.