(1) The way a stream pours forth from a narrow opening, from a narrow place into open country.
(2) To emerge, the way a smaller stream emerges from the landscape and enters a larger stream.
(1) The creek debouched from the hills the way a stream of urine exits from someone who has recently finished eight beers.
(2) I debouched from my tent this morning, because I felt fancy. Usually I'm just groggy, greasy, ornery, and exit like water buffalo droppings.