retractv.缩回;收回;撤销
retract stroke内缩行程
retraction bulb回缩球
retractile disc回缩盘
retractile cord回缩塞绳
retraction rate回缩率
retractor clamp牵引夹
retraction jack升降机
retraction ring收缩环
retracting drop收缩液滴
retraction lock防收锁