An alternate form of “aurochs,” an extinct large long-horned wild ox of Europe that is the ancestor of domestic cattle. I had heard of an aurochs but hadn’t seen this variant.
From the story “Actors” in the collection Dictation by Cynthia Ozick, page 79.
The usage in context here is pretty undistinguished, as the word appears in a list of words that the author of crossword puzzles happens to know. It’s not really worth quoting.