chat-bombing
When you and one or more friend(s) are sitting next to each other on various computers and typing the exact same message to one person on facebook chat, thus confusing the person to tears and/or laughter.
Let's go chat-bombing on Facebook!
chat bomb
When a few/several people send messages to each other in a group chat that there are so many of them (50+ messages is considered a chat bomb.)
Oh god, it's time to scroll up to see what's going on. Why'd they drop that chat bomb?