A cheval \A` che*val"\ [F., 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.
[1913 Webster]
A position [`a] cheval on a river is not one which a
general willingly assumes. --Swinton.
[Webster 1913 Suppl.]