Definition of "insidious" in English

adjective

1. Causing harm in a stealthy, often gradual, manner.

2. Intending to entrap; alluring but harmful.

   • Hansel and Gretel were lured by the witch’s insidious gingerbread house.
   • All these facts clearly appear to me now to establish that the sanctioned scheme was a part of a bigger and […] more insidious scheme which was to hoodwink the creditors and to firmly establish and consolidate the position […]
   • This seemed to her the worst defilement into which this insidious city had cheated her and in her agitation, she nearly ran into the latrine, […]

3. (nonstandard) Treacherous.

   • The battle was lost due to the actions of insidious defectors.