Noun

1. A large cask; an oblong vessel bulging in the middle, like a pipe or puncheon, and girt with hoops; a wine cask.
2. A fermenting vat.
3. An English measure of capacity for liquids, containing 252 wine gallons; equal to two pipes.
   • 1882, James Edwin Thorold Rogers, A History of Agriculture and Prices in England, p. 205:

     Again, by 28 Hen. VIII, cap. 14, it is re-enacted that the tun of wine should contain 252 gallons, a butt of Malmsey 126 gallons, a pipe 126 gallons, a tercian or puncheon 84 gallons, a hogshead 63 gallons, a tierce 41 gallons, a barrel 31.5 gallons, a rundlet 18.5 gallons.

4. A weight of 2,240 pounds.
5. An indefinite large quantity.
6. A drunkard; so called humorously, or in contempt.
7. Any shell belonging to Dolium and allied genera; called also tun-shell.