Related to dim matter: cosmic web, intergalactic space, interstellar medium, intergalactic matter, Intracluster medium
Matter that is presumed to exist because of the gravitational effect it has on other matter but that is difficult to observe directly because of its very low luminosity.
American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.