1.
recoil, reaction, backlash
A force or movement that occurs in response to a prior action, often in the opposite direction. Can be physical or metaphorical.
2.
reactionary (political)
In a political context, opposition to progress or reform, favoring a return to a previous state.
反動 describes a reaction or backlash that occurs in the opposite direction of a prior action. In everyday Japanese, it most commonly refers to a rebound effect — overdoing something after a period of restraint.
Common patterns
- 〜の反動で: as a rebound/backlash from ~
- 反動が来る: to experience a rebound/backlash
- 反動が大きい: the backlash is severe
Common collocations
- ダイエットの反動: rebound from dieting
- 無理した反動: backlash from overexertion
- 反動的: reactionary (na-adjective)
- 反動勢力: reactionary forces (political)
Usage
In everyday conversation, the rebound/backlash sense (sense 1) is far more common. The political sense (reactionary) appears mainly in news and academic writing.