plural of insidiousness

Producing harm in a stealthy, often gradual, manner. / Intending to entrap; alluring but harmful. / (nonstandard) Treacherous.

in an insidious manner

A surreptitious harmfulness, quality of entrapment, or treacherousness; the characteristic of being insidious.

(transitive, obsolete) To lie in ambush for.

(obsolete) One who lies in ambush.

plural of insidiator

simple past tense and past participle of insidiate

Third-person singular simple present indicative form of insidiate