The central rays of light are blocked out by means of an opaque stop while the peripheral rays are reflected from the paraboloidal sides of the condenser and refracted by the object viewed.    From Wordnik.com.  [The Elements of Bacteriological Technique A Laboratory Guide for Medical, Dental, and Technical Students. Second Edition Rewritten and Enlarged.] Reference

Its upper surface is paraboloidal in shape, as a spherical surface will not unite in a sharp focus the rays coming from a distant object.    From Wordnik.com.  [The New Heavens] Reference

When first seen, it wore the aspect of a nebula; later it put on the distinctive garb of a comet; it next appeared as a star; finally, it dilated, first in a spherical, then in a paraboloidal form, until May 5.    From Wordnik.com.  [A Popular History of Astronomy During the Nineteenth Century Fourth Edition] Reference