What is unbeknownst?

Unbeknownst is an adverb that means without the knowledge or awareness of someone. It is often used to describe a situation in which someone does not know that something is happening or has happened. For example, "Unbeknownst to me, my car had a flat tire." or "I was unbeknownst to the fact that the party had been canceled." It can also be used in the form of "unbeknownst to someone else", as in "Unbeknownst to her parents, she had quit her job."