1. emerged or issued from a narrow or confined space into a wide, open area
Usage: often used of troops, rivers, or crowds; military/geographical contexts
2. flowed out or emptied (said of a river or stream) into a larger body of water
Usage: geographical/hydrological term

Examples

• The soldiers debouched from the forest onto the open plain.
• The river debouched into the Atlantic Ocean after a long journey inland.
• Crowds debouched from the stadium after the final whistle.
• The mountain pass debouched into a wide valley.
• Refugees debouched from the narrow canyon into the refugee camp.
• The stream debouched into the larger lake.