reliction

American Heritage® Dictionary of the English Language, Fourth Edition

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

Century Dictionary and Cyclopedia

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

Wiktionary

1. n. the gradual loss of water from a river, lake etc to leave permanent dry land

GNU Webster's 1913

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