Lethe1. (n.) Death.
2. (n.) A river of Hades whose waters when drunk caused forgetfulness of the past.
3. (n.) Oblivion; a draught of oblivion; forgetfulness.
Thesaurus Entries
Lethe, Walter Mitty, absence of mind, absorption, abstractedness, abstraction, bemusement, brown study, carelessness, castle-building, daydream, daydreamer, daydreaming, decay of memory, depth of thought, disregard, disregardfulness, distraction, dream, dreaming, engrossment, fantasy, fantasying, fit of abstraction, flightiness, flippancy, forgetfulness, forgetting, forgiveness, frivolousness, giddiness, hazy recollection, heedlessness, inadvertence, inadvertency, inattention, inattentiveness, inconsideration, incuriosity, indifference, inobservance, levity, lightmindedness, mooning, moonraking, muse, musefulness, musing, muted ecstasy, negligence, nepenthe, nirvana, nonobservance, obliteration, oblivion, obliviousness, pipe dream, pipe-dreaming, preoccupation, regardlessness, reverie, shallowness, short memory, stargazing, study, superficiality, thoughtlessness, trance, unalertness, unawareness, unconsciousness, unheedfulness, unintentiveness, unmindfulness, unobservance, unwariness, unwatchfulness, waters of oblivion, woolgathering