sealed beam
noun1
Engineering, Natural sciences, Physical sciences, Technology A type of electric lamp for producing a beam of light in which the filament is sealed inside a unit consisting of the reflector and lens so as to ensure the alignment of the beam and to protect the reflector from becoming dirty or tarnished.
- The new Sealed Beam Headlights are designed to maintain substantially their initial efficiency throughout their life.1940, Ralph A. Richardson, Optics and Wheels, General Motors Corporation, p. 25