flask UK /ˈflɑːsk/US /ˈflæsk/noun 7verb 1forms 3 noun7 •A narrow-necked vessel of metal or glass, used for various purposes; as of sheet metal, to carry gunpowder in; or of wrought iron, to contain quicksilver; or of glass, to heat water in, etc. •A container used to discreetly carry a small amount of a hard alcoholic beverage; a pocket flask. •Laboratory glassware used to hold larger volumes than test tubes, normally having a narrow mouth of a standard size which widens to a flat or spherical base. •(Newfoundland) A small bottle of liquor. •A nuclear flask, a large, secure lead-lined container for the transport of nuclear material. •A container for holding a casting mold, especially for sand casting molds. •A bed in a gun carriage. verb1 •To invest a denture in a flask so as to produce a sectional mold. formsflasked · flasking · flasks