Stacking of UM or UIM
Auto Insurance
This coverage allows you to either multiply the amount of uninsured or underinsured motorist coverage by the number of vehicles on your policy, or to receive uninsured or underinsured motorist coverage from more than one policy under which you are insured. It costs extra to stack uninsured or underinsured motorist coverage.
- — Auto Insurance Glossary retrieved 2014-05-19