Main Entry: abyss Pronunciation: &-'bis, a- also 'a-(")bis Function: noun Etymology: Middle English abissus, from Late Latin abyssus, from Greek abyssos, from abyssos, adjective, bottomless, from a- + byssos depth; perhaps akin to Greek bathys deep Date: 14th century 1 : the bottomless gulf, pit, or chaos of the old cosmogonies 2 a : an immeasurably deep gulf or great space b : intellectual or moral depths