Mutually destructive; most often applied to warfare.
Characterized by struggle within a group, usually applied to an ethnic or familial relationship.
Extremely hostile or malicious; intensely acrimonious.
Of a pathogen: replicating within its host cell, then immediately causing it to undergo lysis.
Of a disease or disease-causing agent: malignant, able to cause damage to the host.
Of animals, plants, or substances: extremely venomous or poisonous.