a large cask; an oblong vessel bulging in the middle, like a pipe or puncheon, and girt with hoops; a wine cask.-a fermenting vat.-a certain measure for liquids, as for wine, equal to two pipes, four hogsheads, or 252 gallons. in different countries, the tun differs in quantity.-a weight of 2,240 pounds. see ton.-an indefinite large quantity.-a drunkard; -- so called humorously, or in contempt.-any shell belonging to dolium and allied genera; -- called also tun-shell.-to put into tuns, or casks.