- noun (written as side effect)an effect produced by a medical treatment such as a drug, which is not the main effect intended
- (written as side effect)An undesired or indirect consequence caused by an operation, expression, or subroutine. For instance, a change to a variable caused by a function not working directly on it.
- noun (written as side effect)an undesirable secondary effect of a drug or other form of medical treatment
- noun an effect produced by a drug or treatment which is not the main effect intended