a type of electron microscope in which a moving electron beam is used to scan an object causing it to emit secondary electrons which form a pattern that produces a three-dimensional image on the screen of a cathode-ray tube
See scanning electron microscope in American Heritage Dictionary 4
(skănˈĭng)
noun Abbr. SEM
An electron microscope that forms a three-dimensional image on a cathode-ray tube by moving a beam of focused electrons across an object and reading both the electrons scattered by the object and the secondary electrons produced by it.