retractor
/rɪˈtræktə(r)/noun
1- a device for retracting something伸缩装置：
seat belts with automatic retractors.
带自动伸缩装置的座椅安全带。
1.1
- （亦作retractor muscle）chiefly Zoology a muscle serving to retract a part of the body【主动】牵拉肌。比较PROTRACTOR.