probably the great aurochs or wild bulls which are now extinct. The exact meaning is not known.The Vulgate: rinoceros
The Greek OT: μονοκερως (mo-no-keh-rohss)
Jamieson, Fausset,Brown Commentary:
unicorn — Pliny [Natural History, 8.21], mentions such an animal; its figure is found depicted in the ruins of Persepolis. The Hebrew reem conveys the idea of loftiness and power (compare Ramah; Indian, Ram; Latin, Roma). The rhinoceros was perhaps the original type of the unicorn. The Arab rim is a two-horned animal. Sometimes “unicorn” or reem is a mere poetical symbol or abstraction; but the buffalo is the animal referred to here, from the contrast to the tame ox, used in ploughing (Job 39:10, Job 39:12).******
So, what is that all about? Romans? Bull-headed?