plane

plane

noun \ˈplān\

Definition of PLANE

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>