1. To record one's departure from some place in a list, log book, or register. All visitors must sign out of the building when they are leaving. This is a secured area, so you'll need to sign out of the room.

2. To enter someone else's name in a list, log book, or register to record their departure from some place. In this usage, a noun or pronoun is used between "sign" and "out." You'll have to have one of the adjudicators sign you out of the exam room if you need to leave the room. You have to be signed out of the warehouse by one of your supervisors if you need to leave work early.

3. To end one's session in a digital account or network (typically one accessed by having entered personal credentials). Always make sure to sign out of the computers in the library after you are finished. You should always sign out of these websites after you're finished shopping.

4. To end someone else's session in a digital account or network. In this usage, a noun or pronoun is used between "sign" and "out." Don't worry, I went ahead and signed you out of the website. Sorry, I accidentally signed you out of your account on the computer.