idiom · firm and resolute, especially referring to a person's habits or determination that remains unchanged by external circumstances

他每天去公园锻炼身体，雷打不动，已经坚持了二十年。

idiom · describing plans, schedules, or regulations that are fixed and must be followed regardless of the situation

这个会议的时间是雷打不动的，谁都不能更改。