The word "watchmate" generally refers to a companion or colleague with whom one shares the duty of keeping watch or vigilance. Some synonyms for this word include "watch partner," "surveillance buddy," "vigilance ally," "monitoring comrade," and "observation associate." These words convey the same meaning as "watchmate" and can be used interchangeably in different contexts. Other possible synonyms might include "guardian associate," "patrol mate," "sentinel companion," or "security partner." Regardless of the specific term used, the idea remains the same: a person or group of people who share the responsibility of watching over a particular location, individual, or situation.