Culinary definition of melt: To liquify through application of heat.
C@H FOOD FOR THOUGHT
We don't have much to add to the traditional definition, other than advise never to melt chocolate over direct heat, and also warn against melting butter over too high a heat.
Milk solids in butter burn at about 250F (120 C), so use caution. For details on how to properly melt butter to remove the milk solids so that the fat can be cooked at higher temperatures, see Clarify.