n., adj., & v.
n. 1 a a flat surface on which a straight line joining any two points on it would wholly lie. b an imaginary flat surface through or joining etc. material objects. 2 a level surface. 3 colloq. = AEROPLANE. 4 a flat surface producing lift by the action of air or water over and under it (usu. in comb.: hydroplane). 5 (often foll. by of) a level of attainment, thought, knowledge, etc. 6 a flat thin object such as a tabletop.
adj. 1 (of a surface etc.) perfectly level. 2 (of an angle, figure, etc.) lying in a plane.
v.intr. 1 (often foll. by down) travel or glide in an aeroplane. 2 (of a speedboat etc.) skim over water. 3 soar. plane chart a chart on which meridians and parallels of latitude are represented by equidistant straight lines, used in plane sailing. plane polarization a process restricting the vibrations of electromagnetic radiation, esp. light, to one direction. plane sailing 1 the practice of determining a ship's position on the theory that she is moving on a plane. 2 = plain sailing (see PLAIN(1)). plane-table a surveying instrument used for direct plotting in the field, with a circular drawing-board and pivoted alidade.
[ L planum flat surface, neut. of planus PLAIN(1) (different. f. PLAIN(1) in 17th c.): adj. after F plan, plane ]