Definition of "plain clothes" [plain clothes]

• Civilian clothes worn by someone in an occupation or organization for which a uniform might be expected, as the police or clergy. (noun)

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• "'This morning two plain clothes officers of the Metropolitan Police went to Ellis Quint's flat overlooking Regent's Park intending to interview him harmlessly about his whereabouts early Saturday morning."
• "Gager, during his conference with his colleague Bunfit, had been dressed in plain black clothes; but in spite of his plain clothes he looked every inch a policeman."
• "I was particularly grateful for the fact of being in plain clothes one day though, when, walking along Boulevard Saint-Michel, I heard a voice hailing me."