malignant
1. [ adjective ] (pathology) characterized by progressive and uncontrolled growth (especially of a tumor)
Examples:

"a malignant tumor"

Related terms: benign pathology malign cancerous
2. [ adjective ] extremely malevolent or malicious
Synonyms: malevolent
Examples:

"the malignant tongues of gossipers"

Related terms: malign
Similar spelling:   malignantly
  malign
  malignment
  malignancy
  malignance
  malignity
  maligner
  maligned