A TCP/IP socket. The "raw" refers to the socket itself where one might program directly to the socket without going through the TCP/IP programming interface.
"raw socket." YourDictionary, n.d. Web. 10 June 2018. <http://www.yourdictionary.com/raw-socket>.
raw socket. (n.d.). Retrieved June 10th, 2018, from http://www.yourdictionary.com/raw-socket