English vocabulary · C1
Insidious
/ɪnˈsɪd.i.əs/ · adj.
It means causing harm slowly and in a hidden way. The danger is there, but you cannot see it.
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Example sentences
- The drug had an insidious effect on his mind.
- Her insidious lies slowly broke the team apart.
Word origin and roots
from Latin
- in — into (from Latin)
- sedere — to sit (from Latin)
Synonyms and nuances
- SUBTLE — hard to detect (Quiet & Hard to Notice)
- SNEAKY — acting in secret (Hidden on Purpose)
- COVERT — done in secret (Deliberately Concealed)
Words with the same root
sed — to sit
- reside — to live in a place
- session — a period of activity
- sedentary — sitting down too much
Lesson notes
Insidious. It means causing harm slowly and in a hidden way. The danger is there, but you cannot see it.
Similar words are subtle, sneaky, and covert. Use insidious when hidden harm grows slowly over time.
The drug had an insidious effect on his mind. Her insidious lies slowly broke the team apart.
From Latin. in- means into. Sedere- means to sit. Something that sits inside, waiting — that is insidious.