adjective
1.
free from all ostentation or superficial embellishment
just give the plain facts
Synonyms: discreet, dry, homely, inelaborate, modest, simple, unadorned, unbeautified, undecorated, unelaborate, unembellished, unembroidered, ungarnished, unornamented, unostentatious, unpretentious
Related Word: muted, restrained; austere, bald, bare, severe, spartan, stark, unluxurious; homespun
Contrasted words: adorned, beautified, elaborate, embellished, embroidered, exaggerated; high-flown, ostentatious, pretentious; flamboyant, rococo
Antonyms: rich
2.
Synonyms: straight 3, neat, pure, unadulterated, undiluted, unmixed
3.
Synonyms: clear 5, apparent, distinct, evident, manifest, obvious, palpable, patent, unambiguous, unequivocal
Related Word: broad, unmistakable; legible
Antonyms: abstruse
4.
Synonyms: frank , candid, open, openhearted, straightforward, unconcealed, undisguised, undissembled, undissembling, unvarnished
Related Word: unfeigned; abrupt
Idioms: plain and open
5.
lacking allure without being positively ugly
a plain woman, drably dressed
Synonyms: homely, unalluring, unattractive, unbeauteous, unbeautiful, uncomely, unhandsome, unpretty
Related Word: plain-featured; inelegant; ordinary, plain Jane, unremarkable; ill-favored
Idioms: not much for looks, not much to look at, short on looks
Contrasted words: alluring, attractive, beautiful, comely, handsome; elegant; striking; knockout, sensational
6.
Synonyms: ordinary 1, everyday, plain Jane, quotidian, routine, unremarkable, usual, workaday