Individuals and families fleeing densely populated areas and cities in the event of a societal collapse, looting all in their path. Most of these people will not know how to survive without a Walmart or McDonald's so they will likely pillage and loot the surrounding countryside as the cities will have likely succumbed to chaos and rioting.

The act of throwing away hoarded items in your home or various places.

The act of playing on a drum set without considering the people around you. Drum Hoarders typically frustrate company due to the volume of play or the lack of giving other people a turn.
A Drum Hoarder does not have to be good at playing drums; they only play it for a very long period of time, typically with company.
Drum Hoarding also relates to people who spend a large amount of time trying demo drum sets at a store, oblivious to the people possibly waiting in line for a turn.

The act of taking or buying another's previously hoarded items for the purposes of your own hoarding.

Any person who owns more than 2 dogs.

When something (usually in a group of things) is so awesome that it makes everything around it seem bad. This cool thing could be described as "hoarding teh awesome."

passive aggressive hoarding
when someone very subtly and gradually builds up a small area in the home or office of random useless bits of junk, but since it is just one area and relatively small it may not get noticed by others until it's too late and grown in size.