ə̇nˈsidēəs sometimes -ijəs adjective
Etymology: Latin insidiosus insidious, cunning, deceitful, from insidiae ambush + -osus -ous
1.
a. : watching for an opportunity to ensnare
an insidious tempter
: lying in wait : intended to entrap or trick
an insidious plot
b. : enticing and deleterious
these insidious drugs
2.
a. : acting by imperceptible degrees : having a gradual, cumulative, and usually hidden effect : subtle
insidious charm
the insidious pressures of modern life
an insidious drink
b. of a disease : developing so gradually as to be well established before becoming apparent
Synonyms: see sly