BOGON

"Bogon" is an informal name for an IP packet on the public Internet that claims to be from an area of the IP address space reserved, but not yet allocated or delegated to any organization by the Internet Assigned Numbers Authority (IANA) or a delegated Regional Internet Registry (RIR). The areas of unallocated address space are called "bogon space".

Simply, IP address which is currently not assigned to any Internet User, But reserved for future allocation called BOGON.

Somebody think that BOGON list is a IP block list, which is not usable or assigned to anyone and also the 'Private IP Block' which is reserved for private use.

IANA has reserved 3 block of IP for private & non Internet use, IP address which is under the IP range:

10/8 (10.0.0.0 to 10.255.255.255)
172.16.0.0/12 (172.16.0.0 - 172.31.255.255)
192.168.0.0/16 (192.168.0.0 to 192.168.255.255)

is not under BOGON list.

In one word, IP which has not been assigned to anyone, not even under Private network IP block and having a chance to assigned in future is called BOGON.

For more Information on Bogon List, Keep an eye on this page, I will add more and more information on 'BOGON' List.