Having the character of a plane; contained within a plane: as, a plane mirror; a plane curve.In botany, having a flat surface or surfaces.In entomology, flat and not deflexed; flat at the margins: as, plane elytra.n. A geometrical surface such that if any two points in it are joined by a straight line, the line will lie wholly on the surface; a surface such that two of them which have any three points in common must coincide over their whole extent; hence, a real surface having (approximately) this form.n. Specifically In biology: An ideal surface of extension in any axis of an organism: as, the vertical longitudinal plane of the body.n. A surface approximately flat or level; a “horizon” : as, the plane of the teeth or of the diaphragm.n. In coal-mining, any slope or incline on which coal is raised or lowered, but usually applied to self-acting inclines, or those on which the coal is lowered by gravity. [Pennsylvania anthracite region.] In England any main road, whether level or inclined, may be called a planen. In crystallography, one of the natural faces of a crystal.n. Figuratively, a grade of existence or a stage of development: as, to live on a higher plane.To make plane or smooth; make clear.To make smooth, especially by the use of a plane: as, to plane wood.To rub out; erase.n. A tool for paring, smoothing, truing, and finishing woodwork.n. A metallic gage or test for a true surface; a true plane or plane surface; a surface-plate.n. An instrument, resembling a plasterers' trowel, used by brickmakers for striking off clay projecting above the top of the mold.n. The plane-tree.n. In geometry, a plane through the center of a sphere.n. In linegeom., one of the planes of which two are determined by each straight of the congruence taken with each of the two straights consecutive to it by which it is intersected.n. A wood-working plane having a stock resting on adjustable slides which take the place of the sole, and having adjustable fences on each side of the stock, so as to admit, by the use of various attachments, of the use of a great variety of bits. It can thus be used in molding, matching, beading, reeding, aud fiuting, as a hollow, chamfer-, fillister-, dado-, and slitting-plane, and as a plow. Also called universal plane.