heat up phrasal verbphr v a) HOTto become warm or hot, or to make something become warm or hot （使）变热，（把…）加热 The stove takes a while to heat up. 炉子要过一会儿才能热起来。
heat something ↔ up I heated up the remains of last night’s supper. 我把昨天晚饭剩下的饭菜热了一下。
b) DIFFICULTif a situation heats up, it becomes dangerous or full of problems 〔形势〕激化，加剧，恶化
heat up• The stones heated up in the sun.• As the gas heats up, it expands.• While the oven is heating up, prepare the sauce.
→ heat up at heat2(2)