WordNet sense 1 (applies to nonhuman mammals: a state or period of heightened sexual arousal and activity):

estrus, rut, oestrus

WordNet sense 2 (a form of energy that is transferred by a difference in temperature):

heat energy

WordNet sense 3 (the sensation caused by heat energy):

warmth

WordNet sense 4 (the presence of heat):

hotness, high temperature

WordNet sense 5 (the trait of being intensely emotional):

passion

WordNet sense 6 (utility to warm a building):

heating, heating system, heating plant

WordNet sense 7 (arouse or excite feelings and passions):

ignite, inflame, wake, fire up, stir up

WordNet sense 8 (gain heat or get hot):

heat up, hot up