1. flat surface on which any geometrical line that joins two points can lie (geometry); two-dimensional surface (art); airplane; rank, level; type of tree; bladed tool used to smooth wood. smooth wood using a plane; make smooth, remove rough areas. flat, planar; level, even. planeplane, v. i. of a boat, to lift more or less out of the water while in motion, after the manner of a hydroplane; to hydroplane.plane plane , n. [f., fr. l. platanus, gr. , fr. broad; -- so called on account of its broad leaves and spreading form. see: place, and cf. platane, plantain the tree.] (bot.) any tree of the genus platanus.note: the oriental plane (platanus orientalis) is a native of asia. it rises with a straight, smooth, branching stem to a great height, with palmated leaves, and long pendulous peduncles, sustaining several heads of small close-sitting flowers. the seeds are downy, and collected into round, rough, hard balls. the occidental plane (platanus occidentalis), which grows to a great height, is a native of north america, where it is popularly called sycamore, buttonwood, and buttonball, names also applied to the california species (platanus racemosa).plane plane, n. [f. plane, l. plana. see: plane, v. & a.]