When an unexpected guest shows up unexpectedly and isn't welcome, they can be referred to in various ways. Some synonyms for "unwanted visitor" are intruder, unwelcome guest, uninvited guest, unwanted guest, trespasser, unwanted intruder, gatecrasher, and unwelcome visitor. A person who enters a property without permission or legal right is considered a trespasser, while an unwanted visitor can make one feel uncomfortable and violated. Regardless of the synonym used, an unwanted guest should be dealt with appropriately. If an unwanted guest appears at your door, one should speak to them firmly and kindly to let them know their presence is not welcome.