Entry 1 sense Webster, 1913 Tenebrous /tĕn'-əb-rəs/ · Ten·e·brous · IPA /ˈtɛn.ə.bɹəs/ 01 a. Dark; gloomy; dusky; tenebrious. 1. Dark; gloomy; dusky; tenebrious. “The most dark, tenebrous night.” — J. Hall (1565). “The towering and tenebrous boughts of the cypress.” — Longfellow.