When you want someone to stop moving and stay in one place, there are several synonyms you can use instead of the phrase 'hold still for'. For instance, you can say 'freeze,' which means to stop suddenly and not move at all. You can also say 'stay put' or 'remain stationary' to tell someone to stay in one spot. Another option is to use 'stand still,' which means to stop moving while standing in one place. Alternatively, you can use the phrase 'don't move a muscle,' which is a more dramatic way of telling someone not to move at all. Whatever the phrase you choose to use, it is important to make sure that it is clear enough for the person to understand what you want them to do.