Coastline (noun)

1. The outline of the land along the sea.
2. The boundary between the land and the sea.
3. The length of this boundary.
4. The specific shape of a particular stretch of coastline.
5. The strip of land immediately adjacent to the sea.

Origin:

Coastline is a combination of the words 'coast', which refers to the land along the sea, and 'line', which refers to a long, narrow mark or band.

Examples:

1. The coastline of California is known for its rugged cliffs and beautiful beaches.
2. Many coastal cities are threatened by rising sea levels and erosion along their coastlines.
3. The coastline of Maine is famous for its picturesque lighthouses and rocky beaches.
4. The coastline of the Gulf of Mexico is largely characterized by sandy beaches and marshy wetlands.
5. The coastline of Australia is one of the longest in the world, stretching for over 35,000 kilometers.