1. Knowledge of a person acquired by a relationship less intimate than friendship; a relationship based on such knowledge; a person known to one, but usually not a close friend. : "We struck up an acquaintance with our new neighbor."
2. A person whom one knows; the state of being acquainted.
3. Knowledge or information about something or someone; personal knowledge as a result of study, experience, etc.: "The man obviously has a passing acquaintance with Chinese history."