A person or animal (a consumer, in the ecological sense) which oms and noms. An omnomnivore can be an omnivore, a carnivore, or an herbivore, as long as it oms and/or noms.
Brittany was ravenous. She wolfed down the salad, then the appetizers, then the entrees, then the dessert, then the horses in the barn, and, finally, the cows in the meadow. She sure was a gold star omnomnomavore.