# insidious

Pronunciation: say "in-SID-ee-uhs" /ɪnˈsɪdi.əs/

## Adjective

1. Doing harm in a stealthy, often gradual way that is hard to notice.
   - Simple: Causing harm in a hidden way, often slowly, so people do not notice it.
   - _The disease is insidious, progressing for years before any symptoms appear._
   - _Small daily compromises had a more insidious effect on the team's morale than any single defeat._
2. Designed to entrap, appearing attractive while being harmful.
   - Simple: Made to trick and trap you, looking nice but causing harm.
   - _Cult recruiters use insidious flattery to draw lonely people in._
   - _The ad's insidious promise of quick riches hid the fees buried in the contract._
3. Treacherous and disloyal, ready to betray trust or allegiance. *(nonstandard)*
   - Simple: Not loyal and ready to turn against friends or allies.
   - _The general blamed the defeat on a handful of insidious officers who had switched sides._
   - _The rebels never forgave their insidious allies, who sold their plans to the enemy._

## Origin

From Middle French insidieux, from Latin īnsidiōsus ("cunning, artful, deceitful"), from īnsidiae ("a lying in wait, an ambush, stratagem"), from īnsideō ("to sit in or on"), from in ("in, on") + sedeō ("to sit").

Source: DictionaryAI, https://dictionaryai.com/define/insidious (written from Wiktionary data, CC BY-SA 4.0: https://creativecommons.org/licenses/by-sa/4.0/).