A chat hobum is one of the dozens of people who sit in a chat room and refuse to talk, they often minimize the chat window and forget about it all together. Adversely they sometimes just watch the chat room waiting for girls offering to cyber, rp, or trade pictures.
Koolaid: so you heard the new linkin park album?
radda: of course, it's the sickest!
Koolaid: so there are like 50 people online but we're the only ones talking?
Koolaid: screw you chat server
pandabear: yeah, that bunch of chat hobums!