Webster's Revised Unabridged Dictionary · 1913

Debouch

Debouch , intransitive verb

[French déboucher; pref. dé- (Latin dis- or de) + boucher to stop up, from bouche mouth, from Latin bucca the cheek. Compare Disembogue.]

To march out from a wood, defile, or other confined spot, into open ground; to issue.
Battalions debouching on the plain. — Prescott
2.
(Geography) To issue; -- said of a stream passing from a gorge out into an open valley or a plain.