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".
Someone had to stay at the playground and hold down the fort while the anchor weights were being replaced.
by guyboy625 September 28, 2010
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Taking care of the place you're at while others are gone.
As Sandy was leaving work, she said "hold down the fort" to Jill, who was now working alone.
by ButterflyTrixi June 14, 2006
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