When a person invades a conversation (particularly one that has gone on for a while, and often online for better effect) by saying something odd or funny that relates to the most recent of sentences or subjects, but should be unrelated to most of the conversation as a whole.
Social bombing of any sort can be justified with the simple phrase, "I did it for the lulz."
An example of conversationbombing, however not a very good one.
Person 1: ... And so he was like, "You were right there in my room!" So then she was like, "No, I wouldn't be anywhere near your room!"
Person 2: omg like, wow haha
Conversationbomber: DO NOT WANT.