- sector ► NOUN 1) an area or portion that is distinct from others. 2) a distinct part of an economy, society, or sphere of activity. 3) a subdivision of an area for military operations. 4) the plane figure enclosed by two radii of a circle or ellipse and the arc between them. 5) a mathematical instrument consisting of two arms hinged at one end and marked with sines, tangents, etc. for making diagrams.DERIVATIVES sectoral adjective.ORIGIN Latin, 'cutter' .
English terms dictionary. 2015.