1PHRASAL VERB-ERG (因大笑、剧痛等)(使)弯腰,(使)弓身 If something doubles you up, or if you double up, you bend your body quickly or violently, for example because you are laughing a lot or because you are feeling a lot of pain. (因大笑、剧痛等)(使)弯腰,(使)弓身
...a savage blow in the crutch which doubled him up. [VERB noun PREP.]
对他下身凶狠的一击疼得他直不起腰
They laugh so hard they double up with laughter. [VP + with/in]