CEFR C1

insidious

adjective

Meaning

Stealthy, sneaky, and harmful, often in a way that is not immediately noticeable. Insidious actions or behaviors are designed to undermine or destroy something, such as a person's reputation or a system, by gradual and subtle means.

Examples

  • The insidious effects of the new policy were only apparent after several years.
  • The company's insidious marketing tactics were designed to manipulate consumers into buying more.