Close observation of an individual or group; person or persons under suspicion. / Continuous monitoring of disease occurrence for example.

plural of surveillance

(transitive, US) To keep someone or something under surveillance.

Third-person singular simple present indicative form of surveil

present participle of surveil

simple past tense and past participle of surveil

overseeing; watchful

One who watches over another; an overseer; a spy; a supervisor.

plural of surveillant

Than can be surveilled.