To rob one of something very dear to them by force. Usually something that would leave the victim poor and waif like in the streets searching for food in dumptsers and meaning in life now that they are reaved,
The act of "reaving" usually refers to 'soul reaving.' Souls can be reaved by pretty much any one person or diety that is stronger than its victim. Soul reaving is an irreversible process and souls cannot be returned without consent of the reaver.
"I have come to reave your soul."
"Morgoth the Terrible reaved the souls of all the Gothmog children in the land of the Valarion in the days when the Kurkim still roamed the land."