the world > matter > properties of materials > temperature > heat > action of boiling > boil [verb (intransitive)] > boil up (3)
intransitive. Of a liquid: To bubble up in agitation through the action of heat causing the lowest portions of the liquid to pass into the gaseous…
intransitive. To boil, overheat. Also transitive and in extended use.
intransitive. Of liquid, esp. molten metal: to bubble vigorously as a result of boiling or the release of gases. Obsolete.