1.nounA state of being acquainted with a person; originally indicating friendship, intimacy, but now suggesting a slight knowledge less deep than that of friendship; acquaintanceship.
"I know of the man; but have no acquaintance with him."
2.nounA person or persons with whom one is acquainted.
3.nounSuch people collectively; one's circle of acquaintances (with plural concord).
4.nounPersonal knowledge (with a specific subject etc.).