Definition of "planar" [planar]

• Of, relating to, or situated in a plane. (adjective)
• Flat: a planar surface. (adjective)
• Having a two-dimensional characteristic. (adjective)

American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

• "Contrary to earlier claims, we find that the amount of power concentrated in planar modes for $\ell = 2,3$ is not inconsistent with isotropy and Gaussianity."
• "The construction shows that the wavefronts remain planar."
• "Wikipedia suggests: "Something is called planar if it is made up of flat planes, or pertaining to planes.""