Meaning & use

insidiously

adverb·Advanced

In a way that spreads gradually and causes harm without being noticed until the damage is done.

See it in a sentence

The disease progressed insidiously for years before any symptoms became noticeable.

Corruption had insidiously taken hold of the department long before anyone reported it.

A note on using this word

Insidiously almost always describes something harmful; it is not used for gradual, positive change.

Words with a similar meaning

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

Words with an opposite meaning

openly

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