Free from obstructions; open; clear: in plain view. Obvious to the mind; evident: make one's intention plain. See Synonyms at apparent. Not elaborate or complicated; simple: plain food. Straightforward; frank or candid: plain talk. Not mixed with other substances; pure: plain water. Common in rank or station; average; ordinary: a plain man. Not pretentious; unaffected. Marked by little or no ornamentation or decoration. Not dyed, twilled, or patterned: a plain fabric. Lacking beauty or distinction: a plain face. Sheer; utter; unqualified: plain stupidity. Archaic Having no visible elevation or depression; flat; level. An extensive, level, usually treeless area of land. A broad level expanse, as a part of the sea floor or a lunar mare. Something free of ornamentation or extraneous matter. Informal Clearly; simply: plain stubborn.