| 1. | thorough knowledge or mastery of a thing, subject, etc. |
| 2. | the state of being familiar; friendly relationship; close acquaintance; intimacy. |
| 3. | an absence of ceremony and formality; informality. |
| 4. | freedom of behavior justified only by the closest relationship; undue intimacy. |
| 5. | Often, familiarities. an instance of such freedom, as in action or speech. |
| 6. | a sexual liberty or impropriety. |