plane

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun Mathematics A surface containing all the straight lines that connect any two points on it.
• noun A flat or level surface.
• noun A level of development, existence, or achievement.
• noun An airplane or hydroplane.
• noun A supporting surface of an airplane; an airfoil or wing.
• adjective Mathematics Of or being a figure lying in a plane.
• adjective Flat; level. synonym: level.
• noun A carpenter's tool with an adjustable blade for smoothing and leveling wood.
• noun A trowel-shaped tool for smoothing the surface of clay, sand, or plaster in a mold.
• intransitive verb To smooth or finish with a plane.
• intransitive verb To remove with a plane.
• intransitive verb To work with a plane.
• intransitive verb To rise partly out of the water, as a hydroplane does at high speeds.
• intransitive verb To soar or glide.
• intransitive verb To travel by airplane.
• noun The plane tree.

from The Century Dictionary.

• To make smooth, especially by the use of a plane: as, to plane wood.
• To rub out; erase.
• noun 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.
• 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.
• noun 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.
• noun Specifically In biology: An ideal surface of extension in any axis of an organism: as, the vertical longitudinal plane of the body.
• noun A surface approximately flat or level; a “horizon” : as, the plane of the teeth or of the diaphragm.
• noun 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 plane
• noun In crystallography, one of the natural faces of a crystal.
• noun Figuratively, a grade of existence or a stage of development: as, to live on a higher plane.
• noun In geometry, a plane through the center of a sphere.
• noun 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.
• To make plane or smooth; make clear.
• noun The plane-tree.
• noun A tool for paring, smoothing, truing, and finishing woodwork.
• noun A metallic gage or test for a true surface; a true plane or plane surface; a surface-plate.
• noun An instrument, resembling a plasterers' trowel, used by brickmakers for striking off clay projecting above the top of the mold.

from the GNU version of the Collaborative International Dictionary of English.

• transitive verb To make smooth; to level; to pare off the inequalities of the surface of, as of a board or other piece of wood, by the use of a plane.
• transitive verb To efface or remove.
• transitive verb rare Figuratively, to make plain or smooth.
• noun (Bot.) Any tree of the genus Platanus.
• noun (Geom.) A surface, real or imaginary, in which, if any two points are taken, the straight line which joins them lies wholly in that surface; or a surface, any section of which by a like surface is a straight line; a surface without curvature.
• noun (Astron.) An ideal surface, conceived as coinciding with, or containing, some designated astronomical line, circle, or other curve
• noun (Mech.) A block or plate having a perfectly flat surface, used as a standard of flatness; a surface plate.
• noun (Joinery) A tool for smoothing boards or other surfaces of wood, for forming moldings, etc. It consists of a smooth-soled stock, usually of wood, from the under side or face of which projects slightly the steel cutting edge of a chisel, called the iron, which inclines backward, with an apperture in front for the escape of shavings
• noun (Surv.) the horizontal plane upon which the object which is to be delineated, or whose place is to be determined, is supposed to stand.
• noun See Perspective.
• noun (Geom.) a plane in which points infinitely distant are conceived as situated.
• noun the cutting chisel of a joiner's plane.
• noun (Opt.) See Polarization.
• noun (Descriptive Geom.) One of the planes to which points are referred for the purpose of determining their relative position in space.
• noun (Opt.) the plane in which lie both the incident ray and the refracted or reflected ray.