Being familiar is a common trait that refers to recognizing and knowing someone or something well. However, there are several antonyms for this word that reflect a lack of familiarity or knowledge. Unfamiliar is a term that means not recognizing or being unacquainted with someone or something. Unacquainted also represents the concept of not being familiar with someone or something. Alien and unknown are two other antonyms that can be used to describe lack of familiarity. Overall, these antonyms convey a sense of unfamiliarity or lack of knowledge, which can make it challenging to connect with people or understand new things.