is a multicast
addressing method for IPv4
networks that is defined in RFC 2770
GLOP is not an actual acronym
: it is a term that was chosen by the authors of the RFC, who were at a loss for a better term.
GLOP numbering sets the first octet of the address to 233, the second two octets to the registered Autonomous System value, and the fourth octet is locally assigned.
GLOP addresses are used by ISPs who want to provided multicast content on the Internet.
You can lookup your GLOP address space via this web tool