n. A person who eats whatever he or she can find, particularly food that has been discarded.
Forget buying brie from local producers. Or stocking up on strictly organic oranges. Or even insisting on cruelty-free tofu chops instead of four-legged fry-ups. The latest wave of ethical eaters are opting out of the grocery-food chain entirely — and into dumpster dining.

Called freegans, urban foragers, opportunivores, these social activists are so repulsed by the food waste in developed countries — and the larger politics of the food industry — they rifle through trash cans to salvage "corporate leftovers" for their meals.
—Jenn Gearey, “Consumed with less: not buying any food,” The Globe and Mail, January 13, 2007
What the housemates will eat, though, are dumpster finds, like the three half-pound bags of shredded coconut that they rescued from the trash bin behind a health food store. When I first arrived at the house, Josh was bent over a laptop, scouring the Internet for recipes containing coconut — the housemates were organizing a brunch the next day, and the coconut was already a month stale, so they needed to get rid of it. The recipe hunt was made more difficult because four of the housemates are vegans, meaning they won't eat any sort of animal product; two of the housemates are vegetarians, and Nate's an opportunivore, meaning that he'll eat anything that's around.
—Kate Swearengen, “Activism, Princeton-style,” Princeton Alumni Weekly, February 26, 2003
1998 (earliest)
The Ju/'hoansi still hunt and gather in Nyae Nyae, formerly Namibia's Eastern Bushmanland. In "opportunivore" style, they are using their traditional skills to enter the global cash economy.
—Ted Kerasote, “Be an opportunivore; What American sportsmen can learn from African bushmen,” Sports Afield, August 01, 1998
'I enjoy eating meat occasionally,' she explained, 'but I don't have to feel guilty about it, because I never buy it myself. I only eat meat when it is cooked for me by my friends.' And she added, with just a hint of smugness, 'I like to call myself an opportunivore.'
—Hugh Fearnley Whittingsall, “Cowardly carnivore,” The Evening Standard, May 27, 1997