in·sid·i·ous /ɪnˈsɪdiəs/
  (a.)隱伏的,陰險的,狡猾的
  in·sid·i·ous /ɪnˈsɪdɪəs/ 形容詞
  隱襲的,隱匿的
  In·sid·i·ous a.
  1. Lying in wait; watching an opportunity to insnare or entrap; deceitful; sly; treacherous; -- said of persons; as, the insidious foe. “The insidious witch.”
  2. 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.
  Syn: -- Crafty; wily; artful; sly; designing; guileful; circumventive; treacherous; deceitful; deceptive.
  -- In*sid*i*ous*ly, adv. -- In*sid*i*ous*ness, n.
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  insidious
       adj 1: beguiling but harmful; "insidious pleasures"
       2: intended to entrap
       3: working or spreading in a hidden and usually injurious way;
          "glaucoma is an insidious disease"; "a subtle poison"
          [syn: pernicious, subtle]