(COMPLETE) [adjective] [before noun; not gradable] - (used for emphasis) completeIt was just plain luck that I ran into her in town, and she told me about this job.Well that was a plain waste of time, wasn't it?The plain truth is that we can't afford to pay anymore.
PLAIN
Meaning of PLAIN in English
Cambridge English vocab. Кембриджский английский словарь. 2012