adv. phr. arch. [A prep.1 of state, on + HORSEBACK.] On horseback.
1490. Caxton, Eneydos, li. 145. Whan he was sette ahorsbacke.
1665–9. Boyle, Occas. Refl., II. ix. (1675), 126. The careless Wanderer … may be said to have been long a Horse-back.
1771. Smollett, Humph. Cl. (1815), 189. There were two suspicious fellows a-horseback at the end of a lane.
1852. Thackeray, Esmond, I. v. (1876), 35. And he never was known to wear his silk, only his stuff one, a-horseback.
