1. To keep a fort from flying away when the fort has such a low density that it tends to float off.
2. To take care of a place while someone who is usually there is
gone, such as a store or one's home.
When unsure as to which
definition should be applied, it can help to judge the person's intelligence - morons usually
mean #2. A less moronic term for #2 would be "to hold the fort".