The mouth. Someone considered to be well-endowed in this department may have it said of him that he has a mooth like the Clyde Tunnel. A person who has irregular or stained teeth may be described as having a mooth like a row of condemned hooses or buildings.
One of the unpleasant after-effects of a heavy drinking session, especially when mixed with smoking is a mooth like a pocket of douts (cigarette butts). A similar expressing is a mooth like a badger’s bum or arse. One can’t help but wonder why a badger should be considered particularly unpleasant in this department and indeed, how anyone found out.
The phrase you’ve a mooth indicates an offer of food or drink to a guest:
“Ye know, Ah sat in the hoose for a good hoor an’ a hauf, an’ they never thought tae say, ye’ve a mooth.”