: bad or unfavorable : not good
adverse criticism/remarks
He had an adverse reaction to the medicine. [=he reacted badly to the medicine; the medicine had a bad effect on him]
Many fear that budget cuts will have an adverse [=damaging] effect on education.
adverse circumstances/conditions/weather
The drug has no adverse [=harmful] side effects.
Cite this Entry
“Adverse.” Merriam-Webster.com Simple Definition, Merriam-Webster, https://www.merriam-webster.com/simple/adverse. Accessed 14 Apr. 2026.
Copy Citation
