double-jointed

详细解释:a. 双关节的, 可前后自由活动的

英语解释：

形容词 double-jointed:

having unusually flexible joints especially of the limbs or fingers

详细解释：

dou.ble-joint.ed

adj.（形容词）
Having unusually flexible joints, especially of the limbs or fingers.
双关节的：尤指四肢或手具有异常柔韧关节的