Accoridng to newsday (via), a freegan is:

"Freegan" comes from the term vegan - a person who does not eat meat or animal products for health or ethical reasons. Freegans take it one step further by eating food thrown away by stores and restaurants, to avoid waste and limit their impact on the environment. They say that by not buying food, they're boycotting a capitalist consumer society that needlessly slaughters animals and harms the environment by mass-producing nonessential food, much of which ends up in landfills.

That reminds me the proles in Bruce Stlering's novel Distraction who create/recycle their own food...