Main Entry: plane

Pronunciation: \ˈplān\

Function: noun

1 a : a surface that contains at least three points not all in a straight line and is such that a line drawn through any two points in it lies wholly in the surface b : an imaginary plane used to identify parts of the body or a part of the skull—see frankfort horizontal plane, midsagittal plane
2 : a stage in surgical anesthesia <a light plane of anesthesia is maintained with cyclopropane—Journal of the American Medical Association>