A microscope with high-intensity illumination used to study very minute objects, such as colloidal particles that scatter the light and appear as bright spots against a dark background. (noun)
American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.