(un-, prefix1 affix 2. Sense doubtful.)

Of horses: Not broken in; untamed. Obsolete.

Of horses, etc.: Not tamed or rendered tractable; untrained.

Of a horse: not properly broken in; unruly, not easily ridden. Also in figurative contexts.

Of horses, etc.: Not broken in; untamed.

Of horses: Unmounted; untrained.

Of an animal, esp. a horse, or of a person: not (yet) trained. Cf. made, adj. 5.

= unbroken, adj. 4.

Of horses and cattle: Apt to break fences, and get out of enclosures.

U.S. Of a horse: that is an outlaw (outlaw, n. 3b). rare.