plainer

adjective, plain·er, plain·est.

1. clear or distinct to the eye or ear: a plain trail to the river; to stand in plain view.
2. clear to the mind; evident, manifest, or obvious: to make one’s meaning plain.
3. conveying the meaning clearly and simply; easily understood: plain talk.
4. downright; sheer; utter; self-evident: plain folly; plain stupidity.
5. free from ambiguity or evasion; candid; outspoken: the plain truth of the matter.
6. without special pretensions, superiority, elegance, etc.; ordinary: plain people.
7. not beautiful; physically unattractive or undistinguished: a plain face.
8. without intricacies or difficulties.
9. ordinary, simple, or unostentatious: Although she was a duchess, her manners were attractively plain.
10. with little or no embellishment, decoration, or enhancing elaboration: a plain blue suit.
11. without a pattern, figure, or device: a plain fabric.
12. not rich, highly seasoned, or elaborately prepared, as food: a plain diet.
13. flat or level: plain country.
14. unobstructed, clear, or open, as ground, a space, etc.
15. Cards. being other than a face card or a trump.

adverb

16. clearly and simply: He’s just plain stupid.

noun

17. an area of land not significantly higher than adjacent areas and with relatively minor differences in elevation, commonly less than 500 feet (150 meters), within the area.
18. The Plains. Great Plains.

adjective

1. flat or smooth; level
2. not complicated; clearthe plain truth
3. not difficult; simple or easya plain task
4. honest or straightforward
5. lowly, esp in social rank or education
6. without adornment or showa plain coat
7. (of fabric) without pattern or of simple untwilled weave
8. not attractive
9. not mixed; simpleplain vodka
10. knitting of or done in plain

noun

11. a level or almost level tract of country, esp an extensive treeless region
12. a simple stitch in knitting made by putting the right needle into a loop on the left needle, passing the wool round the right needle, and pulling it through the loop, thus forming a new loop
13. (in billiards)
    1. the unmarked white ball, as distinguished from the spot balls
    2. the player using this ball
14. (in Ireland) short for plain porter, a light portertwo pints of plain, please

adverb

15. (intensifier)just plain tired

verb

1. a dialect or poetic word for complain

adj.c.1300, “flat, smooth,” from Old French plain “flat, smooth, even” (12c.), from Latin planus “flat, even, level” (see plane (n.1)). Sense of “evident” is from, c.1300; that of “free from obstruction” is early 14c.; meaning “simple, sincere, ordinary” is recorded from late 14c., especially of dress, “unembellished, without decoration.” In reference to the dress and speech of Quakers, it is recorded from 1824; of Amish and Mennonites, from 1894 (in the Dutch regions of Pennsylvania Plain with the capital is shorthand adjective for “Amish and Old Order Mennonite”). Of appearance, as a euphemism for “ill-favored, ugly” it dates from 1749. Of envelopes from 1913. As an adverb from early 14c. Plain English is from c.1500. Plain dealer “one who deals plainly or speaks candidly” is from 1570s, marked “Now rare” in OED 2nd edition. To be as plain as the nose on (one’s) face is from 1690s. n.“level country,” c.1300 (in reference to Salisbury Plain), from Old French plain “open countryside,” from Latin planum “level ground, plain,” noun use of neuter of planus (adj.) “flat, even, level” (see plane (n.1)). Latin planum was used for “level ground” but much more common was campus.

1. An extensive, relatively level area of land. Plains are present on all continents except Antarctica and are most often located in the interior regions. Because they can occur at almost any altitude or latitude, plains can be humid and forested, semiarid and grass-covered, or arid.
2. A broad, level expanse, such as an area of the sea floor or a lunar mare.

In addition to the idioms beginning with plain

plain as day

plain sailing

also see:

in plain English