1. A hearing impairment consisting of an inadequate reception of sounds to the ears; partial deafness: The doctor told Etta that she had hypacusis which is why she was having so much trouble hearing what the speakers on her TV were saying and finding it necessary to ask people to repeat what they had just said because she simply could not hear everything that was spoken.
2. Etymology: from Greek hypo-, "under, less than" + Greek akousis, "hearing".