A word or phrase is pejorative if it expresses contempt or disapproval about the thing or person described. Most pejorative expressions may also be used in a non-pejorative way, however, and (as with any implied meaning) determining the intent of the speaker is problematic.
Although pejorative means the same thing as disparaging, the latter term may be applied to a look or gesture as well as to words and phrases.
Sometimes a term may begin as a pejorative word and eventually grow to have a non-pejorative sense.