A term that means "over" as in, "I am now waiting for your reply/answer." I remember saying "over" on the CB radio. KKK was used in teletype communication, for example:
John, will I see you tomorrow at the camp site? kkk
Yes Bill, I will be waiting for you. kkk
Ok John, then see you tomorrow. kkk
Now it's morphed into online jargon, also known as text message shorthand, used in texting, online chat, instant messaging, email, blogs, and newsgroup postings, these types of abbreviations are also referred to as chat acronyms.