Webster's Revised Unabridged Dictionary · 1913

A cheval

A cheval

[French, lit., on horseback.]

Astride; with a part on each side; -- used specif. in designating the position of an army with the wings separated by some line of demarcation, as a river or road.
A position à cheval on a river is not one which a general willingly assumes. — Swinton