tun /tʌn/noun 12verb 1forms 4 noun12 •A large cask; an oblong vessel bulging in the middle, like a pipe or puncheon, and girt with hoops; a wine cask. (See a diagram comparing cask sizes.) •A fermenting vat. •(historical) A traditional unit of liquid measure (from the volume of such a cask) equal to 252 wine gallons or 2 pipes. •(Malaysia) A respectful term of address to royalties and certain award recipients •The cryptobiotic state of a tardigrade, when its metabolism is temporarily suspended. •Any shell belonging to Tonna and allied genera. •A part of the ancient Maya Long Count Calendar system which corresponds to 18 winal cycles or 360 days. •Synonym of long ton: a unit of mass equal to 2240 pounds, 20 hundredweights of 112 pounds avoirdupois each. •(figurative) Synonym of ton: any extremely or excessively large amount.He therefore sends you, meeter for your spirit, / This tun of treasure; and, in lieu of this, / Desires you let the dukedoms that you claim / Hear no more of you. — 1599 •(dialect, UK) a chimney. •(disapproving, no longer used) Synonym of drunkard: a person who drinks excessively. •(no longer used) A small silver cup holding half a pint, sometimes having a whistle in the handle that could not be blown until the cup was empty.So abundant is the supply of tankards and "tuns" […] — 1900 verb1 •To put into tuns, or casks. formstunned · tunning · tuns · tunob