Plain intransitive verb [OE. playne, pleyne, fr. F. plaindre. See Plaint.] To lament; to bewail; to complain. [Archaic & Poetic] Milton.

We with piteous heart unto you pleyne. Chaucer.

Plain, transitive verb To lament; to mourn over; as, to plain a loss. [Archaic & Poetic] Sir J. Harrington.

Plain, adjective [comparative Plainer; superlative Plainest.] [F., level, flat, fr. L. planus, perhaps akin to E. floor. Cf. Llano, Piano, Plan, Plane level, a level surface.]

1. Without elevations or depressions; flat; level; smooth; even. See Plane.

The crooked shall be made straight, and the rough places plain. Isa. xl. 4.

2. Open; clear; unencumbered; equal; fair.

Our troops beat an army in plain fight. Felton.

3. Not intricate or difficult; evident; manifest; obvious; clear; unmistakable. “’T is a plain case.” Shak.

4. (a) Void of extraneous beauty or ornament; without conspicious embellishment; not rich; simple.

(b) Not highly cultivated; unsophisticated; free from show or pretension; simple; natural; homely; common. “Plain yet pious Christians.” Hammond. “The plain people.” A. Lincoln.

(c) Free from affectation or disguise; candid; sincere; artless; honest; frank. “An honest mind, and plain.” Shak.

(d) Not luxurious; not highly seasoned; simple; as, plain food.

(e) Without beauty; not handsome; homely; as, a plain woman.

(f) Not variegated, dyed, or figured; as, plain muslin.

(g) Not much varied by modulations; as, a plain tune.

Plain battle: open battle; pitched battle [Obs.] Chaucer.

Plain chant (Mus.): Same as Plain song, below.

Plain chart (Naut.): a chart laid down on Mercator's projection.

Plain dealer

(a) One who practices plain dealing

(b) A simpleton [Obs.] Shak.

Plain dealing: See under Dealing.

Plain molding (Join.), molding of which the surfaces are plain figures.

Plain sewing: sewing of seams by simple and common stitches, in distinct from fancy work, embroidery, etc.; – distinguished also from designing and fitting garments.

Plain song

(a) The Gregorian chant, or canto fermo; the prescribed melody of the Roman Catholic service, sung in unison, in tones of equal length, and rarely extending beyond the compass of an octave

(b) A simple melody.

Plain speaking: plainness or bluntness of speech. > Syn. – Level; flat; smooth; open; artless; unaffected; undisguised; frank; sincere; honest; candid; ingenuous; unembellished; downright; blunt; clear; simple; distinct; manifest; obvious; apparent. See Manifest.

Plain, adverb In a plain manner; plainly.

“To speak short and pleyn.” Chaucer.

“To tell you plain.” Shak.

Plain, noun [Cf. OF. plaigne, F. plaine. See Plain, adjective]

1. Level land; usually, an open field or a broad stretch of land with an even surface, or a surface little varied by inequalities; as, the plain of Jordan; the American plains, or prairies.

Descending fro the mountain into playn. Chaucer.

Him the Ammonite
Worshiped in Rabba and her watery plain. Milton.

2. A field of battle. [Obs.] Arbuthnot.

Lead forth my soldiers to the plain. Shak.

Plain, transitive verb [imperfect or past participle Plained; present participle or verbal noun Plaining.] [Cf. Plane, verb]

1. To plane or level; to make plain or even on the surface. [R.]

We would rake Europe rather, plain the East. Wither.

2. To make plain or manifest; to explain.

What's dumb in show, I'll plain in speech. Shak.

-- Websters 1913