Insidious
Definition 1 of 2
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Hidden Harm
Use 'insidious' for problems that worsen without obvious symptoms. The spy's insidious sabotage went unnoticed until it was too late.
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Slow Progression
Describes something harmful developing gradually, which may be difficult to detect initially. Climate change is an insidious threat that evolves over decades.
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Cultural Nuance
'Insidious' is often used to describe sly tactics or conspiracies in movies and literature. The insidious plot of the villain in the novel kept readers on edge.