1.
to turn over in bed, to roll over in one's sleep
To change one's sleeping position by rolling to one side. A natural movement during sleep.
赤ちゃんが寝返った。
The baby rolled over.
寝返るたびに目が覚めてしまう。
I wake up every time I turn over in bed.
腰が痛くて夜中に何度も寝返った。
My back hurt, and I tossed and turned many times during the night.
2.
to defect, to switch sides, to betray
To abandon one's allegiance and join the opposing side. Used for political, military, or organizational betrayals.
敵に寝返る。
To defect to the enemy.
味方だと思っていた部下が寝返った。
A subordinate I thought was on my side switched sides.
戦国時代には、家臣が敵方に寝返ることは珍しくなかった。
During the Warring States period, it was not uncommon for retainers to defect to the enemy.
CONJUGATION:
Godan verb (五段動詞), る-ending.
- Negative: 寝返らない
- Polite: 寝返ります
- Te-form: 寝返って
- Past: 寝返った
USAGE:
Sense 1 is the literal meaning (rolling over in sleep). The related noun 寝返り means "rolling over" and is commonly used in baby development (赤ちゃんの寝返り). Sense 2 is figurative — betraying one's group to join the opposition.
COMMON COLLOCATIONS:
- 寝返りを打つ: to toss and turn
- 敵に寝返る: to defect to the enemy
- 赤ちゃんが寝返る: a baby rolls over