Plain, a. [Compar. Plainer superl. Plainest.]
 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.”
 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.