a boundary line between land and water
"The children played along the rocky shoreline where the ocean met the sand."
The divide between land and a body of water.
"After walking along the rocky shoreline, we watched the waves crash against the sand where the sea meets the land."
In plain English: The shoreline is where land meets water, such as at the edge of an ocean beach or lake shore.
"We spent the afternoon building sandcastles along the rocky shoreline."
Usage: Use "shoreline" to refer specifically to the boundary line where land meets water, rather than using it as a synonym for the beach itself or the general coastal area. Avoid confusing it with "seashore," which often implies the sandy expanse available for recreation in addition to the edge of the water.
The word shoreline is a straightforward combination of the words shore and line. It was formed to describe the specific boundary where the land meets the water.