1. Descriptive of someone who is deviating from what is considered to be proper or from an expected course of action: Timothy's aberrant personality frequently got him into trouble with his employers.

Driving on the wrong side of a road is considered an aberrant driving practice and will result in a traffic ticket or may even cause a serious accident.

2. Not the ordinary, usual, or normal type; exceptional; abnormal: In circuses of the last century, there were often displays of pitiful animals that were aberrant in some way, like having an extra toe, a double tail, or more than one head.