pejorative

from The American Heritage® Dictionary of the English Language, 5th Edition.

  • adjective Disparaging; belittling.
  • noun A disparaging or belittling word or expression.

from The Century Dictionary.

  • Tending or intended to depreciate or deteriorate, as the sense of a word; giving a low or bad sense to.
  • noun In grammar, a word that depreciates or deteriorates the sense: thus, poetaster is a pejorative of poet, criticaster of critic.