From Longman Dictionary of Contemporary Englishldoce_107_cflaskflask /flɑːsk $ flæsk/ noun [countable] 1 
British EnglishDFU a special type of bottle that you use to keep liquids either hot or cold, for example when travelling SYN Thermos2 DFUa hip flask3 HCa glass bottle with a narrow top, used in a laboratory
British EnglishDFU a special type of bottle that you use to keep liquids either hot or cold, for example when travelling SYN Thermos2 DFUa hip flask3 HCa glass bottle with a narrow top, used in a laboratoryExamples from the Corpus
flask• Brown headlands, ribbons of current, purple and turquoise waters clear as a flask all shivered and dazzled.• Another takes a sip from a flask in a paper bag.• They even shared cream cakes and tea from a flask at half-time.• Angus thought everyone looked so chilly that he shivered in sympathy and took a swallow from his flask.• What collectors refer to as historical flasks are glass bottles blown into metal molds between about 1815 and 1870.• Alternatively the embryo culture dishes can be placed in sealed flasks pre-equilibrated with a mixture of 5% CO2 in air.• He drank some whisky from the flask in his pack.Origin flask (1300-1400) Late Latin flasco 