hot upvi phrasalphrasal verb, intransitive: Verb with adverb(s) or preposition(s), having special meaning and not taking direct object--for example, "make up" [=reconcile]: "After they fought, they made up."
slang, figurative (become more exciting)
变得更激烈，变得更激动人心
We're into the final week of the election campaign. Things are about to hot up around here.