Lying in wait; watching an opportunity to insnare or entrap; deceitful; sly; treacherous; -- said of persons; as, the insidious foe. "The insidious witch." Cowper.
Intended to entrap; characterized by treachery and deceit; as, insidious arts. The insidious whisper of the bad angel. Hawthorne. Insidious disease (Med.), a disease existing, without marked symptoms, but ready to become active upon some slight occasion; a disease not appearing to be as bad as it really is.
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