Because of the weaknesses in both the carnivore and omnivore terms (as I understand it, carnivores don't tend to eat underground storage organs, even those which are edible raw, or nuts, whereas our ancient ancestors did and most human cultures have, plus omnivore is a vague term that tends to be used as an excuse to eat whatever someone wants and seems to give people the impression that humans can quickly adapt to novel foods), so currently I'm using the term "adaptivore." It accounts for more of the foods that humans and proto-humans ate than facultative carnivore and it gives more of a sense that it can take a long time to adapt to novel foods and that there are differences in adaptation between different human populations (Inuit vs. Japanese, for example). So I'm leaning to "adaptive" as the answer to the question in the thread title.
Here's an example of what I mean about the misuse of the term "omnivore" to justify biologically inappropriate diets:
"Dogs are classified in the order Carnivora, but, unlike cats (a topic for another day) they have evolved biologically as omnivores, meaning their systems can derive nutrients from a wide variety of sources, including fruits, vegetables, grains, legumes and animal products." http://www.cnn.com/2011/LIVING/03/10/vegan.dog.diet/index.html?hpt=C2
Note: dogs are facultative carnivores, not omnivores, but ignorant humans have come to misapply the moniker "omnivore" to any creature that eats any plant food, and then justify "plant-based" diets on that skimpy basis.