Source : WordNet®

heat up
     v 1: gain heat or get hot; "The room heated up quickly" [syn: {heat},
           {hot up}] [ant: {cool}]
     2: make hot or hotter; "heat the soup" [syn: {heat}] [ant: {cool}]
     3: make more intense; "Emotions were screwed up" [syn: {hot up},
         {screw up}]