reliction

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun Gradual recession of water in a sea, lake, or stream, leaving permanently dry land.

from The Century Dictionary.

• noun In law, the recession of the sea or other body of water from land; also, land thus left uncovered.

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

• noun (Law) A leaving dry; a recession of the sea or other water, leaving dry land; land left uncovered by such recession.

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

• noun the gradual loss of water from a river, lake etc to leave permanent dry land