• round glass bottle with a long narrow neck (used in laboratory experiments); small glass or metal bottle with a screw-on lid; box, container (used in casting metal)
• a flask is a bottle used for carrying alcoholic or hot drinks around with you.
• you can use flask to refer to a container for liquids and its contents, or to the contents only.
• vessel for boiling fluids in a laboratory
• laboratory flask with a narrow neck and a wide base that is used to mix fluids (designed by richard august carl emil erlenmeyer)
• a hip flask is a small metal container in which brandy, whisky, or other spirits can be carried, usually in the pocket of a jacket.
• a vacuum flask is a container which is used to keep hot drinks hot and cold drinks cold. a vacuum flask has two thin silvery glass walls with a vacuum between them.