know (someone or something) by sight(redirected from know someone or something by sight)
know (someone or something) by sight
To recognize someone or something based on its or their appearance, but without knowing its or their name or any other information. Everyone in town knows the iconic bridge by sight, but few know the history of when it was built and why it was designed to look so peculiar. Even after working there for a year, there were still some co-workers whom I only knew by sight.
know someone by sight
to recognize a person's face, but not know the name. I'm afraid I don't know her by sight. I know all my employees by sight.
know by sight
Recognize someone or something by appearance but not know the name or other details. For example, I know a lot of people by sight from the tennis courts. [1200s]