An assailant is someone who physically attacks another person. If someone suddenly punches, shoves, or tries to harm you without warning, that person is your assailant. Police officers use this word when describing someone who committed a violent crime against another person.

An assailant might be a stranger who attacks someone on the street, or could be someone the victim knows. When witnesses describe a crime to police, they might say “the assailant was wearing a red jacket” or “the assailant fled on foot.”

Unlike words like “opponent” or “rival,” which suggest more equal competition, assailant specifically means someone who attacks first, often when the victim isn't expecting it or can't defend themselves. A boxer who throws punches in the ring isn't an assailant because both fighters agreed to compete. But someone who attacks an unsuspecting person is an assailant because they're using violence inappropriately and often illegally.

The word carries a serious tone because it describes serious situations. You'll most often encounter it in news reports about crimes or in detective stories where characters are trying to identify who attacked someone.