n.
(1) A clause in the Constitution in which the U.S. government guarantees each state a republican form of government and promises to protect each of the states against invasion and against domestic violence.
(2) A clause in a contract in which one party promises to pay someone else’s obligations if necessary.
The Essential Law Dictionary. — Sphinx Publishing, An imprint of Sourcebooks, Inc. Amy Hackney Blackwell. 2008.