WordNet (r) 3.0 (2006):

hot up
    v 1: gain heat or get hot; "The room heated up quickly" [syn:
         heat, hot up, heat up] [ant: chill, cool, cool
         down]
    2: make more intense; "Emotions were screwed up" [syn: heat
       up, hot up, screw up]
    3: make more powerful; "he souped up the old cars" [syn: soup
       up, hop up, hot up]

Moby Thesaurus II by Grady Ward, 1.0:

69 Moby Thesaurus words for "hot up":
   accelerate, agent provocateur, aggravate, amplify, annoy, augment,
   beef up, blow up, build up, chafe, complicate, concentrate,
   condense, consolidate, cook, deepen, deteriorate, double,
   electric-heat, embitter, enhance, enlarge, exacerbate, exaggerate,
   exasperate, fire, fire up, foment, gas-heat, heat, heat up,
   heighten, hop up, hot, hot-air-heat, hot-water-heat, increase,
   intensify, irritate, jazz up, key up, magnify, make acute,
   make complex, make worse, mull, overheat, preheat, provoke, ramify,
   recook, redouble, reheat, reinforce, sharpen, soup up, sour, steam,
   step up, stoke up, strengthen, superheat, tepefy, triple, warm,
   warm over, warm up, whet, worsen