1 PHRASAL VERB (尤指将已经冷掉的熟食)加热 When you heat something up, especially food which has already been cooked and allowed to go cold, you make it hot. (尤指将已经冷掉的熟食)加热 [Also VERB n PREPOSITION]
2 PHRASAL VERB 激化;加剧;变得激烈(或热烈) When a situation heats up, things start to happen much more quickly and with increased interest and excitement among the people involved. 激化;加剧;变得激烈(或热烈)
3 PHRASAL VERB 变热 When something heats up, it gradually becomes hotter. 变热
SYN warm up, get hotter, become hot, rise in temperature