sea wall

from The Century Dictionary.

• noun A strong wall or embankment on the shore, designed to prevent encroachments of the sea, to form a breakwater, etc. See cut in preceding column.
• noun An embankment of stones thrown up by the waves on a shore.

from the GNU version of the Collaborative International Dictionary of English.

• A wall, or embankment, to resist encroachments of the sea.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun Alternative spelling of seawall.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun a protective structure of stone or concrete; extends from shore into the water to prevent a beach from washing away