POS may refer to any of the following:
1. Short for "Packet Over SONET," see the SONET definition for further information.
2. Short for "Point of Sale," POS is the process of using computer technology to record all pertinent data about an item, normally by scanning the Universal Product Code (UPC) on the item. When the scanner picks up that code, it not only tells the user the price of the item, it also records that item as being sold, so the store's inventory can be updated accordingly.
3. Short for "Piece of S#!^," POS is slang used to describe a poor product or service.
4. Shorthand for "Parent Over Shoulder," POS is a term often used by teens and children in chat rooms as an indication that a parent may be watching them.