Meaning & use

insidious

adjective·Advanced

Proceeding in a gradual, subtle way that causes harm before it is noticed or understood.

See it in a sentence

The disease is especially dangerous because its insidious early symptoms are easy to dismiss.

Insidious rumors slowly damaged her reputation long before she realized what was happening.

A note on using this word

Almost always used negatively, describing harm that spreads quietly, unlike "sudden" or "obvious" dangers.

Words with a similar meaning

stealthytreacherous

Choose a synonym to suit the sentence. Meanings can overlap without being identical.

Words with an opposite meaning

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