When a gas or solid substance liquefies or is liquefied, it changes its form and becomes liquid. Heat the jam until it liquefies You can liquefy the carbon dioxide to separate it from the other constituents. a truck carrying liquefied petroleum gas. to become liquid, or make something become liquid
become liquid or fluid when heated; "the frozen fat liquefied" make (a solid substance) liquid, as by heating; "liquefy the silver" become liquid; "The garden air overnight liquefied into a morning dew