urus

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. An extinct wild ox (Bos primigenius) of Europe, northern Africa, and western Asia, believed to be the ancestor of domestic cattle. Also called aurochs.

Century Dictionary and Cyclopedia

1. n. A kind of wild bull described by Cæsar; the mountain-bull, which ran wild in Gaul at the period of the Roman invasion, but has long been extinct. This is the Bos urus, or B. primigenius, of naturalists, and is also called reem, tur, ur, ure, and ure-ox. The urus had long spreading horns, unlike the European bison (Bison bonasus) or aurochs, and more like ordinary cattle, of which B. primigenius is a presumed ancestral form; but by some misunderstanding the name urus has also attached to the aurochs, a few individuals of which still linger wild, but under protection, in the forests of Lithuania. It has been thought, erroneously, that the “Chillingham cattle,” such as exist in confinement at Chillingham in Northumberland, England, and Hamilton in Lanarkshire, Scotland, are descendants of the animal described by Cæsar. See cut under aurochs.
2. n. [capitalized] A genus of Bovidæ, including the aurochs and extinct bisons: therefore equivalent to Bison as now employed.
3. n. A kind of fossil ox from Eschscholtz Bay, Alaska.

Wiktionary

1. n. The aurochs.

GNU Webster's 1913

1. n. (Zoöl.) A very large, powerful, and savage extinct bovine animal (Bos urus or Bos primigenius) anciently abundant in Europe. It appears to have still existed in the time of Julius Cæsar. It had very large horns, and was hardly capable of domestication. Called also, ur, ure, and tur.

WordNet 3.0

1. n. large recently extinct long-horned European wild ox; considered one of the ancestors of domestic cattle