Synonyms of plain

1 Syllable: frank, veldt, meek, iced, heath, blank, smooth, broad, known, swarth, mead
2 Syllables: sonic, pointblank, upfront, mousier, subpar, merest, purer, neural, meekest, frumpy, patent, seeable, levels, simplex, ho-hum, planer, frumpish, easy, lamber, franker, valley, dowdy, lucid, lowborn, purest, up-front, folksy, blankest, verier, prosy, distinct, smoothed, slender, downright, lowland, candid, hohum, aural, plateau, usual, easiest, obvious, blatant, meadow, level, naive, prosier, plateaux, frumpier, open, frankest, dowdier, dingle, ugliest, direct, uglier, overt, upland, meeker, very, smoother, mere, grassland, prairie, rustic, unspoilt, llano, planed, smoothing, clear-cut, artless, subfusc, sharp-cut, folksier, honest, straight-out, forthright, express, point-blank, simpler, homey, simplest, crashing, blanker, veriest, common, smoothest, spartan, ugly, easier, mousy
3 Syllables: savannah, ignoble, insipid, knowable, plainspoken, ophthalmic, unsubtle, sensory, unvarying, gracile, homely, agrestal, genuine, unblended, dead-level, hearable, silhouetted, whitebread, unjaded, unhidden, viewable, homespun, outspoken, unmixed, subfuscous, unbeauteous, hyaline, faceless, commonest, planate, white-bread, unmingled, explicit, graspable, audible, unblurred, levelling, household, pellucid, familiar, homelier, visible, perspicuous, conspicuous, expanse, leveled, literal, tangible, sincerest, restrained, readable, evident, uncomplex, palpable, tasteless, legible, routine, good-sized, straightforward, transparent, apparent, well-marked, afferent, styleless, bare-faced, heart-to-heart, plain-spoken, bad-looking, unbounded, incomplex, sincere, tableland, formulaic, subnormal, ingenuous, plain-dealing, straight-arrow, manifest, frictionless, unbleached
4 Syllables: openhearted, undesigning, undiluted, uncontrived, unreticent, unassuming, unpretentious, unemphatic, unexciting, unaffected, definite, mirrorlike, forgettable, appreciable, undeviating, unfluctuating, open-and-shut, inconspicuous, self-evident, unaffable, unextreme, gustative, unfinished, audiovisual, discernible, unlabored, unassumed, unappealing, unalluring, unrelieved, inarguable, unmodified, incarnated, featureless, conventional, unconspicuous, arrestive, above-board, rudimental, longanimous, matter-of-fact, uncompounded, gustatory, unaesthetic, unambiguous, well-defined, univocal, noticeable, unresisting, everyday, hard-featured, pasturage, unconcealed, undisguised, unbeautiful, characterless, uncombined, unfulfilled, unassembled, pretenseless, square-shooting, undissembling, cellophane
5 Syllables: undisputable, undistinguished, unnoticeable, unexcessive, unexpansive, definitive, unexceptional, neurological, unembarrassed, unpleasurable, demonstrative, undubitable, unexperienced, unidealistic, unimpressive, unembroidered, incontestable, unremarkable, unnoteworthy, elementary, honest-to-goodness, unassailable, ascertainable, unsentimental, unimpassioned, unostentatious, unembellished, recognizable, unmistakable, comprehensible, unattractive, intelligible, understandable, unequivocal, unprepossessing, establishable, apprehensible, comprehendible, unartificial, undecorated, unornamented, person-to-person
6 Syllables: self-explanatory, unsophisticated, unexaggerated, inelaborate, unelaborate