hot air

基本解释

It uses hot air.
它使用热空气。
“They aren’t selling engines, they are selling hot air out the back of an engine,” says an investment analyst.
一位投资分析家说，“它们不是在售卖引擎，它们卖的是引擎后面排出的热空气。”
But unlike their comrades in that bloody urban battle, the marines now in Afghanistan have, for the most part, thrust their swords into hot air.
但与那场惨烈巷战的战友不同，阿富汗的陆战队这一次，绝大部分时候，把炎热的空气当成了他们的打击目标。

State-owned media quote the president as saying he is dissatisfied with this month's global-warming summit in Copenhagen, calling it "a lot of hot air."
I'm hot, compared to the air of the room, or cold if I'm somewhere that's warm.
我相对于室内的空气是热的，或是冷的如果我呆在一个温暖的地方。
麻省理工公开课 - 热力学与动力学课程节选
But if you touch the valve going into your tire which basically measures the temperature of the air going into your tire, that is getting hot, right.
以至于浑身发热,如果你摸气筒的阀门,相当于近似测量了进入轮胎的气体的温度，它会很热，对吧。
麻省理工公开课 - 热力学与动力学课程节选

But in 2009, some of the big ones rose like a hot air balloon.
FORBES: Do Rising BRIC Interest Rates Mean Big EM Bond Gains?

If something that someone says is hot air, it is not sincere and will have no practical results.

热风
The technology of dehydrating wild rice stem using microwave energy in combination with hot air diying was investigated preliminarily.
利用微波能结合热风干燥对茭白脱水的工艺进行了初步研究。
物理学
热空气