mudflat

Collins Concise English Dictionary © HarperCollins Publishers::

mudflat / ˈmʌdˌflæt/ noun

1. a tract of low muddy land, esp near an estuary, that is covered at high tide and exposed at low tide

WordReference Random House Unabridged Dictionary of American English © 2025

mud′ flat′, 

1. a mud-covered, gently sloping tract of land, alternately covered and left bare by tidal waters.
2. the muddy, nearly level bed of a dry lake.
• 1805–15