1. To march out (as from a wood, defile, or other narrow or confined spot) into the open.
2. To emerge; to issue.
To cause to emerge or issue; to discharge.
Debouch comes from French déboucher, from dé- (for de), "out of" (from Latin de) + bouche, "mouth" (from Latin bucca, "cheek, mouth"). The noun form is debouchment.