Definition of Impervious: Impervious (adjective): Unable to be affected by; not allowing something, such as water or light, to pass through. Synonyms: impenetrable, impermeable, resistant, unaffected Antonyms: permeable, vulnerable, receptive, sensitive Memory Tip: Think of “impervious” as “impermeable,” something that doesn’t let anything through or isn’t affected by external forces. Conversation and Short Story Examples…