As a Noun: 1. The condition of knowing something or someone already because you have met, seen or been told about them. English = familiarity. As a Verb or Adjective: 1. To know something or someone already because you have met, seen or been told about them before. English = (be) familiar with. Interactive: 1. Used alone in reply to someone who tells you something you know already, especially when you think they should know you know because it is old news. As Modifier: 1. Used at the beginning of a sentence to introduce a new topic of conversation, especially a person or bit of news, which you are sure the person knows about already.