【原】blow hot and cold，忽冷忽热

要形容一个人行为或是情绪不稳定的，可以用单词 unstable，还可以使用类似意思的习语 blow hot and cold，它的字面意思是“吹热和冷”，那就是忽冷忽热的意思，可以意为”拿不定主意，反复无常“，寓意：

to sometimes like or be interested in something or somebody and sometimes not

有时喜欢某事或某人，有时不喜欢

to change mood frequently about something or someone

经常改变对某事或某人的情绪

used to express frustration that a potential partner seems sometimes to invite and sometimes to reject offers of friendship  or love.

用来表达挫败感，即潜在的伴侣反复无常的表现

例如：

Why are you blowing hot and cold simultaneously? Tell me clearly whether you want to go with it or not.

你为什么总是拿不定主意？清楚地告诉我你是否愿意。

解析：whether 引导的宾语从句。

Her boyfriend keeps running hot and cold whenever she asks him to marry her.

无论何时她要求她男朋友娶她时，他总是拿不定主意。

解析：引导让步状语从句，表示“无论何时”，相当于 at whatever time, no matter when 等。

I really like him, but I'm confused. He seems to blow hot and cold - one minute he likes me, and the next, he's ignoring me!

我真的很喜欢他，但我很困惑。他好像拿不定主意，前一分钟他喜欢我，下一分钟他就不理我了！

I don't think it's fair when people blow hot and cold, and don't tell you clearly what they want.

当有人拿不定主意，并且不能准确地告诉你他们的需求时，我认为是不公平的。

解析：此句是否定转移的用法，形式上否定主句的谓语 think，实际上是否定从句的谓语 is，翻译的时候要按实际的否定来翻译。

人都有情绪化的时候，要相互理解，设身处地，不要在有情绪的时候，做任何决定。这个习语跟 betwixt 和 between 的意思很类似，可以结合起来记忆。