plain-clothes

/plˈeɪnklˈəʊðz/

/plˈeɪnklˈoʊðz/

[adjective]

plain-clothes

[ADJECTIVE]

(of a police officer) dressed in civilian clothes while on duty

Examples

1. The program he found consisted of 1500 plain-clothes intelligence officers who infiltrated every demonstration in the United States of more than 20 people in the 1960's.