Heat that cannot be detected. The heat that enters a system when ice melts to form water or when water boils to form steam is latent heat, because there is no change in the temperature of the system. See sensible heat.
Heat that does not cause a temperature change.
Heat that is absorbed without causing a rise in temperature. For example, "latent heat of vaporization" refers to the amount of heat required to convert a liquid to vapor at a particular temperature.