working against gravity (= the force that attracts objects towards one another, especially the force that makes things fall to the ground), or having the opposite effect to gravity

He says that one day we will all have anti-gravity machines allowing us to zoom up into the sky. 他说，会有那一天，我们将拥有超越地心引力的机器，让我们可以遨游到天空。

They theorized that 70 percent of the universe must be composed of an anti-gravity force called dark energy. 他们推测宇宙的70%须由一种称为暗能量的反引力组成。

according to some scientific theories or in stories, a force that has the opposite effect to gravity (= the force that attracts objects towards one another, especially the force that makes things fall to the ground)

Just as normal attractive gravity slows the expansion of the universe, anti-gravity accelerates it. 正如正常的引力会减慢宇宙的膨胀一样，反引力会加速宇宙膨胀。

In my dream I glide up a flight of steps, suspended in midair by anti-gravity. 在梦中，我滑行了一段台阶，靠反重力悬浮在半空中。