Wiktionary
heat of fusion
n. (context physics English) The amount of heat absorbed by unit mass of a material, at its melting point, that causes a phase transition from solid to liquid
WordNet
heat of fusion
n. heat absorbed by a unit mass of a solid at its melting point in order to convert the solid into a liquid at the same temperature; "the heat of fusion is equal to the heat of solidification"
Usage examples of "heat of fusion".
No material object could withstand the searing heat of fusion bombs and high energy lasers.