1. To have someone stay at a particular location or place: Medical personnel were posted nearby in case there was an emergency.

The officials were posting the police to control the demonstrators.

2. To put in an assigned place: Captain Jones will post at least two soldiers at each gate of the military base on Tuesday.

Guards were posted at all of the doors of the hotel while the visiting head of the foreign country was there.

3. Keeping another person or people informed: Alice told her uncle that she would keep him posted about her travel plans.
4. Etymology: the original meaning of these verbs is "position where someone is placed" and it indicates its Latin source of ponere, "to put, to place".