† imˈplain,v.Obs.rare—1. [f. im-1 + ? plain a., in sense ‘plane, flat, level’.] trans. To make smooth with plaster; to plaster smooth. c1420Pallad. on Husb. i. 479 Oyl dregges mixt with clay thou must implayne [v.r. me may ymplayn] Thi wowes [= walls] with.