Mouth formation is a term used to describe the shape of a river's mouth, which is the point where it empties into a larger body of water. The two crossword solutions for this term are DELTA (5 letters) and Riverdelta (10 letters). A DELTA is a triangular area of land formed by sediment deposits at the mouth of a river. It is typically found in areas with low-lying terrain and is often associated with flooding. Riverdelta is a combination of the words 'river' and 'DELTA, ' and is used to refer to a DELTA that is formed by a river.