n. 1 a distinct part or branch of an enterprise, or of society, the economy, etc. 2 Mil. a subdivision of an area for military operations, controlled by one commander or headquarters. 3 the plane figure enclosed by two radii of a circle, ellipse, etc., and the arc between them. 4 a mathematical instrument consisting of two arms hinged at one end and marked with sines, tangents, etc., for making diagrams etc. sectoral adj.
[ LL, techn. use of L sector cutter (as SECTION) ]