The term "is guest" can be replaced with various synonyms, depending on the context of the situation. One alternative could be "visitor," which is commonly used to describe someone who is not a permanent resident but is temporarily present in a particular location. Another option is "houseguest," which specifies that the individual is staying in someone else's home. "Guest of honor" is another synonym, used to describe a person who is being formally recognized or celebrated at an event. "Invited guest" specifies that the person has been formally invited to attend, while "surprise guest" refers to someone who arrived unexpectedly. Overall, the term "is guest" can be effectively substituted with a variety of synonyms to convey a more specific meaning.