'heat up' definitions:

Definition of 'heat up'

(from WordNet)
verb
Gain heat or get hot; "The room heated up quickly" [syn: heat, hot up, heat up] [ant: chill, cool, cool down]
verb
Make hot or hotter; "the sun heats the oceans"; "heat the water on the stove" [syn: heat, heat up] [ant: chill, cool, cool down]
verb
Make more intense; "Emotions were screwed up" [syn: heat up, hot up, screw up]