The phrase "scaring pants off of" is often used to describe a situation in which someone is frightened or intimidated to an extreme degree. There are several other synonyms that can be used to convey the same meaning. For example, one could say that someone "terrified" them, "shook them to their core," or "made their blood run cold." Other options include "petrified," "horrified," "spooked," "startled," and "freaked out." All of these phrases convey a sense of intense fear or discomfort and can be used interchangeably with "scaring pants off of".