The Collaborative International Dictionary of English v.0.48:
Plane \Plane\, a. [L. planus: cf. F. plan. See Plan, a.]
Without elevations or depressions; even; level; flat; lying
in, or constituting, a plane; as, a plane surface.
Note: In science, this word (instead of plain) is almost
exclusively used to designate a flat or level surface.
Plane angle, the angle included between two straight lines
in a plane.
Plane chart, Plane curve. See under Chart and Curve.
Plane figure, a figure all points of which lie in the same
plane. If bounded by straight lines it is a rectilinear
plane figure, if by curved lines it is a curvilinear plane
Plane geometry, that part of geometry which treats of the
relations and properties of plane figures.
Plane problem, a problem which can be solved geometrically
by the aid of the right line and circle only.
Plane sailing (Naut.), the method of computing a ship's
place and course on the supposition that the earth's
surface is a plane.
Plane scale (Naut.), a scale for the use of navigators, on
which are graduated chords, sines, tangents, secants,
rhumbs, geographical miles, etc.
Plane surveying, surveying in which the curvature of the
earth is disregarded; ordinary field and topographical
surveying of tracts of moderate extent.
Plane table, an instrument used for plotting the lines of a
survey on paper in the field.
Plane trigonometry, the branch of trigonometry in which its
principles are applied to plane triangles.