This relatively new word is a combination of free and vegan. A freegan could be vegetarian or vegan or even meegan, meaning he eats meat. He eats food that is freely available to protest against the exploitative food system. This way of life involves eating discarded foods from dumpsters or wherever you get food for free. You can also use the word as an adjective- so you can attend a freegan wedding or receive a freegan package, which basically means food that is being provided to avoid wastage.
Learn more about freeganism here.