plainclothes

Adjective

not-comparable of a police officer usually

(usually of a police officer) Wearing ordinary civilian clothes instead of a uniform, in order to avoid detection.

Japanese Meaning

（主に警察官が）制服ではなく一般市民の服装を着用して、身を隠すための格好をすること

The plainclothes detective blended into the crowd to observe the suspects.

その刑事は発見を避けるために私服を着て群衆に溶け込み、容疑者を観察した。

Sense（1）

(usually of a police officer) Wearing ordinary civilian clothes instead of a uniform, in order to avoid detection.