Source : Webster's Revised Unabridged Dictionary (1913)

Debouch \De*bouch"\, v. i. [imp. & p. p. {Debouched}; p. pr. &
   vb. n. {Debouching}.] [F. d['e]boucher; pref. d['e]- (L. dis-
   or de) + boucher to stop up, fr. bouche mouth, fr. L. bucca
   the cheek. Cf. {Disembogue}.]
   To march out from a wood, defile, or other confined spot,
   into open ground; to issue.

         Battalions debouching on the plain.      --Prescott.

Debouch \De*bouch"\, v. i. (Geog.)
   To issue; -- said of a stream passing from a gorge out into
   an open valley or a plain.

Source : WordNet®

debouch
     v 1: march out (as from a defile) into open ground; "The
          regiments debouched from the valley" [syn: {march out}]
     2: pass out or emerge; especially of rivers; "The tributary
        debouched into the big river"