Frequency: The word is one of the 3000 most common words in English.
1.
If you describe someone or something as ~, you mean that nobody knows who or what they are.
He was shot this morning by ~ intruders at his house.
...~ cancer-causing substances in the environment.
= unknown
ADJ: usu ADJ n
2.
If you use ~ to describe people, groups, and organizations, you do not want to give their names. (JOURNALISM)
...his claims, which were based on the comments of anonymous and ~ sources.
= unnamed
ADJ: usu ADJ n