Unicorn in Easton's Bible Dictionary

described as an animal of great ferocity and strength (Num. 23:22, R.V., "wild ox," marg., "ox-antelope;" 24:8; Isa. 34:7, R.V., "wild oxen"), and untamable (Job 39:9). It was in reality a two-horned animal; but the exact reference of the word so rendered (reem) is doubtful. Some have supposed it to be the buffalo; others, the white antelope, called by the Arabs rim. Most probably, however, the word denotes the Bos primigenius ("primitive ox"), which is now extinct all over the world. This was the auerochs of the Germans, and the urus described by Caesar (Gal. Bel., vi.28) as inhabiting the Hercynian forest. The word thus rendered has been found in an Assyrian inscription written over the wild ox or bison, which some also suppose to be the animal intended (comp. Deut. 33:17; Ps. 22:21; 29:6; 92:10).

Read More about Unicorn in Easton's Bible Dictionary