Emily Dickinson Lexicon

PLANE, n. [from L. planus. See Plain.]

1. In geometry, an even or level surface, like plain in popular language.
2. In astronomy, an imaginary surface supposed to pass through any of the curves described on the celestial sphere; as, the plane of the ecliptic; the plane of a planet's orbit; the plane of a great circle.
3. In mechanics. [See Plain figure.]
4. In joinery and cabinet work, an instrument consisting of a smooth piece of wood, with an aperture, through which passes obliquely a piece of edged steel or chisel, used in paring or smoothing boards or wood of any kind.