malignant

Etymology

From Middle French malignant, from Late Latin malignans. See malign.

adj

1. Harmful, malevolent, injurious.
   malignant temper; malignant revenge; malignant infection
   […]while, I fear, there will be some white ones, unable to forget that, with malignant heart, and deceitful speech, they have strove to hinder it. 26 August 1863, Abraham Lincoln, Letter to James Conkling, page 7
2. (medicine) Tending to produce death; threatening a fatal issue.
   malignant diphtheria
   a malignant tumor
   “[…] the awfully hearty sort of Christmas cards that people do send to other people that they don't know at all well. You know. The kind that have mottoes[…]. And then, when you see [the senders], you probably find that they are the most melancholy old folk with malignant diseases. […]” 1922, Ben Travers, chapter 1, in A Cuckoo in the Nest

noun

1. A deviant; a person who is hostile or destructive to society.
   As devout Stephen was carried to his burial by devout men, so is it just and equal that malignants should carry malignants […] 1823, The Retrospective Review, volume 7, page 11
   A malignant in a position of real power immediately becomes a tyrant. 1999, National Institute of Business Management, Difficult People at Work, page 8
2. (historical, derogatory, obsolete) A person who fought for Charles I in the English Civil War.