WordValeinsidious
spreading harm subtly and gradually
In more detail
1. (adjective) spreading or developing gradually and quietly, causing harm in a way that is not easy to notice at first
2. (adjective) deliberately designed to harm or deceive someone in a hidden way
Examples
- 1. The insidious effects of climate change are becoming more visible each year.
- 2. The company used insidious tactics to steal their competitors' secrets.
How to use insidious
Insidious describes something harmful that progresses quietly and is difficult to detect until significant damage is done. It emphasizes the hidden, gradual nature of harm and often carries a note of deliberate deception. Use it when the danger lies partly in how unnoticed the problem becomes, distinguishing it from merely subtle (which may not be harmful) or sneaky (which may be temporary or less serious).
Common phrases
- insidious threat
- insidious disease
- insidious influence
- insidious effect
- spread insidiously
Synonyms
subtle · stealthy · sneaky · deceptive · pernicious
Opposites
obvious · overt · transparent
Word family
insidiously (adverb) · insidiousness (noun)
A common mistake
Learners sometimes use insidious simply to mean 'secret' or 'hidden' without the crucial element of harm or damage; the word specifically conveys something harmful that progresses undetected.
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