noun
: an epithet applied to a person or group in order to degrade, blacken, or make unjust or unfounded accusations
time was … when independents in politics were rare and mugwump was a smear word — W.E.Binkley
strained relations may be expressed in clique formation, subtle whispers and shrugs, smear words, discrimination in clubs and dances — F.J.Brown & J.S.Roucek