Noun
Verb (する, intransitive)
1. opposition; rebellion; revolt; resistance; backlash; refusal
もちろん反発の声はすぐに上がった。Of course, voices of opposition immediately rose.
2. rebounding; recoiling; repulsion
バネの反発を利用して高く跳ぶ。You use the spring's rebound to jump high.
3. rally (e.g. in stock prices); recovery