Restiff, n.
A restive or stubborn horse. [Obs.]
1 other Webster entry under this spelling
Restiff, a.
Restive. [Obs.]
Shades of meaning
Fernald has no entry of its own for restiff; he lists it under restive.
Where he writes about it:
Dryden speaks of "the pampered colt" as "restiff to the rein;" but the rein is not used to propel a horse forward, but to hold him in, and it is against this that he is "restiff." A horse may be made restless by flies or by martial music, but with no refractoriness; the restive animal impatiently resists or struggles to break from control, as by bolting, flinging his rider, or otherwise. — from restive