Synonyms for Aurochs (same or very similar meaning)
WordNet sense 1 (European bison having a smaller and higher head than the North American bison):
wisent, Bison bonasus
WordNet sense 2 (large recently extinct long-horned European wild ox; considered one of the ancestors of domestic cattle):
urus, Bos primigenius
From the ODE community, based on WordNet
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