If you're talking about some actor/singer who used to be very popular but not anymore, you can say: He/She is a goner/has-been. He/She is over the hill. If you're talking about fashion, you can say, It's out (of date/fashion). It's not in/trendy anymore. 我看了一下問題的標籤，發現有「所用語言：中文(普通話)」，那我就用中文提一下。 講人過氣的話可以說： He/She is a goner/has-been. (goner 和 has-been 都是指已經風光過了的人) He/She is over the hill. (over the hill 是「越過了山丘」，就是走下坡的意思) 講東西過氣 (不再流行) 的話，可以說： It's out (of date/fashion). It's not in/trendy anymore. out 就是出去了，沒有清楚的上下文時可以再補充是從哪兒出去 (of date/fashion)。 in 是 out 的相反，所以自然就有「時興；流行」的意思。Trendy 是符合潮流。 加上 「不再；not...anymore」就也是「過氣」了。

Out-of-date has other synonyms like obsolete,outmoded. By the way,if my memory serves me,in the film Flashbacks of a Fool I heard the an actor said so "You are over" to Daniel Craig while the Chinese subtitle revealed "你过气了".But I really have no idea if this could be the exact answer to your question cause I have found no "过气" in my dictionary. There could be other opinions. *Now I see.So "you are over" could be the fragemertary form of "you are over the hill".

Out of date/season

Out of date(Fashion)..