Definition of Pernicious: Pernicious (adjective): Having a harmful effect, especially in a gradual or subtle way. Synonyms: harmful, damaging, destructive, deleterious Antonyms: beneficial, harmless, helpful, constructive Memory Tip: Think of “pernicious” as something that slowly eats away at something good, like a disease that spreads unnoticed until it’s too late. Conversation and Short Story Examples…