A brain zap when taking antidepressant medication is essentially a zap or electrical shock or buzz that your brain causes you to feel in your head periodically.
Other ways to describe brain zaps from antidepressants are head shocks, brain shocks or brain shivers.
The brain zaps are a common side effect of withdrawing from antidepressant medications although some people say that they feel brain zaps sometimes when taking antidepressants.