Passer (noun)

1. A person or thing that passes by.
2. A passerby.

Origin:

Late middle english (denoting a person who passes by, or a bird that passes overhead): from pass, in the sense "go by".

Examples:

1. A passer-by called the police when they saw the accident.
2. The passer stopped to watch the street performer.
3. The passer-by didn't notice the pickpocket steal his wallet.
4. The passer hesitated to enter the dark alley.
5. The passer gave a friendly wave as they walked by.