to collect large amounts of something and keep it for yourself, often in a secret place:
During the siege people began hoarding food and supplies.
There would be enough food on a daily basis if people were not hoarding.
to keep a large number of things that are not needed or have no value, because you are suffering from a mental condition:
She hoarded dirty bottles, old newspapers, broken appliances, even plastic bags from cereal boxes.
Psychiatrists are not sure what makes a person start hoarding.