Entry 3 senses · 2 variants Webster, 1913 Lethe /(lē"thē̇ [or] lēth)/ · Le·the · IPA /ˈliːθi/ n. n. 01 n. Death. 1. Death.[Obs.] 02 n. A river of Hades whose waters when drunk caused forgetfulness of the past. 1. A river of Hades whose waters when drunk caused forgetfulness of the past.(Class. Myth.) 2. Oblivion; a draught of oblivion; forgetfulness.