1formal Worsening, deterioration; (sometimes) specifically depreciation, disapproval, criticism; an instance of this; a depreciatory or critical expression.
The development of a less favourable meaning or of less pleasant connotations for a word or expression.
Mid 17th century; earliest use found in Edward Phillips (b. 1630), writer and biographer. From post-classical Latin peioration-, peioratio deterioration from peiorat-, past participial stem of peiorare + classical Latin -iō.