“咬紧”的英语可以翻译为：[医]clench ...

他咬紧骨头,使劲地嚼.He closed his jaws on the bones and crunched.在被动手术时她咬紧了牙关.She clenched her teeth when she was operated on.他咬紧牙齿,灰色的眼光里闪出了坚决的意志.He set his teeth and his gray eyes fairly snapped their determination....