1. the pronoun of the second person singular or plural, used of the person or persons being addressed, in the nominative or objective case: You are the highest bidder. It is you who are to blame. We can't help you. This package came for you. Did she give you the book?
2. one; anyone; people in general: a tiny animal you can't even see.
3. (used in apposition with the subject of a sentence, sometimes repeated for emphasis following the subject): You children pay attention. You rascal, you!
4. Informal. (used in place of the pronoun your before a gerund): There's no sense in you getting upset.