plainer

1. comparativecomparative form of plain: more plain

   Of the two, she was certainly the plainer.

plural plainers

1. A policeman who wears plainclothes.

   A guy and a girl make ideal plainers; nobody gives them a second thought; people just assume they're a couple.

   2022, Niall Illingworth, Hard Rain, Cold Hearts

   2 more examples

   Three pandas were parked round the edge of the wee swing park, lights spinning, flashing blue on a huddle of plainers over by the iron roundabout.

   2018, Alan Parks, Bloody January

   The plainer, he was from the Marine police station on Anderson Street and Davin or Devine or something was his name — said nothing.

   2022, Liam McIlvanney, The Heretic, page 18