Any area, populated or not, which is consistently hotter than the surrounding area. / Ellipsis of urban heat island..

heat generated by the fermentation of tan bark waste; generally used in horticulture as a source of bottom heat for potted plants in greenhouses; the application of tan heat to greenhouse plants, mainly during the 18-19th century.

(horticulture) heat supplied from below to the roots or rooting medium of plants under propagation, usually in hothouses or greenhouses

(physics) The capability of a system to absorb heat energy; the amount of thermal energy required to raise the temperature of a system by one temperature unit without any change of phase.

the heat capacity (specific heat) of humid air, expressed per unit mass of dry air in the mixture. The engineering symbol is cₛ.

(thermodynamics) An object, system or environment that absorbs and dissipates heat from objects in thermal contact (either direct or radiant) with it.

(idiomatic) a close race or contest in which no winner is apparent

(idiomatic) A period of exceptionally hot weather. / (US, weather broadcasting) Three consecutive days with daytime high temperature of 90 degrees Fahrenheit or higher.

(informal) To take the blame; to be the focus of anger or scrutiny; to take the consequences.

(physics) the heat that is released or absorbed accompanying a change of state or of phase