Meaning of side effect

side' effect"

Pronunciation: [key]
  1. any effect of a drug, chemical, or other medicine that is in addition to its intended effect, esp. an effect that is harmful or unpleasant.
  2. any accompanying or consequential and usually detrimental effect: the side effects of air pollution.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.