ten·e·brous (t?n??-br?s) also te·neb·ri·ous (t?-n?b?r?-?s)adj. Dark and gloomy.[Middle English, from Old French tenebreus, from Latin tenebr?sus, from tenebrae, darkness.]ten?e·bros?i·ty (-br?s??-t?) n.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.