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.tenebrous (?t?n?br?s) or tenebriousadjgloomy, shadowy, or dark[C15: from Latin tenebr?sus from tenebrae darkness] tenebrosity, ?tenebrousness, te?nebriousness nCollins English Dictionary ? Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014ten?e?brous (?t?n ? br?s) also te?neb?ri?ous (t??n?b ri ?s) adj. dark; gloomy; obscure. [1375?1425; late Middle English