adj. plain·er, plain·est
1. Free from obstructions; open; clear: in plain view.
2. Obvious to the perception or mind; evident: make one's intention plain. See Synonyms at apparent.
a. Not elaborate or complicated; simple: plain food.
b. Marked by little or no ornamentation or decoration: plain garb.
c. Straightforward; frank or candid: plain talk.
d. Not pretentious; unaffected.
e. Lacking beauty or distinction: a plain face.
4. Not mixed with other substances; pure: plain water.
5. Common in rank or station; average; ordinary: a plain man.
6. Not dyed, twilled, or patterned: a plain fabric.
7. Sheer; utter; unqualified: plain stupidity.
8. Archaic Having no visible elevation or depression; flat; level.
a. often plains An extensive, level, usually treeless area of land.
b. A broad level expanse, as a part of the sea floor or a lunar mare.
2. Something free of ornamentation or extraneous matter.
Clearly; simply: plain stubborn.
[Middle English, from Old French, from Latin plānus; see pelə-2 in the Appendix of Indo-European roots.]
Synonyms: plain, modest, simple, unpretentious
These adjectives mean not ornate, ostentatious, or showy: a plain hairstyle; a modest cottage; a simple dark suit; an unpretentious country church.
The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2018 by Houghton Mifflin Harcourt Publishing Company. All rights reserved.