- Lying in wait; watching an opportunity to insnare or
entrap; deceitful; sly; treacherous; -- said of persons; as, the
insidious foe. - Intended to entrap; characterized by treachery and
deceit; as, insidious arts.
Meaning of 'insidious' (Princeton's WordNet)
1 . insidious
[ s]
Meaning (1): - working or spreading in a hidden and usually injurious way