(astronomy) The plane that passes through the Earth's equator, or by extension the equators of other celestial bodies.

(astronomy) The ecliptic, the plane of the Earth's orbit around the Sun, or by extension the orbital planes of other celestial bodies.

A mirror with a flat surface (i.e. the surface is a single plane)

An aircraft used for surveillance.

(nautical) A diving plane mounted on or near the bow of a submarine.

(nautical) A diving plane mounted on or near the stern of a submarine.

(nautical) A moveable control surface on a submarine, used to control the depth and pitch of the submarine.

(nautical) A diving plane mounted on or near the sail of a submarine, used to cause the submarine to rise or sink without pitching up or down.

(physics) polarized light in which the electric and magnetic fields vibrate in same phase

A sycamore maple (Acer pseudoplatanus), native to North America.