Spam, definition of (partial, from Wikipedia)
"According to the Internet Society and other sources, the term spam is derived from the 1970 SPAM sketch of the BBC television comedy series "Monty Python's Flying Circus".
The sketch is set in a cafe where nearly every item on the menu includes SPAM canned luncheon meat. As the waiter recites the SPAM-filled menu, a chorus of Viking patrons drowns out all conversations with a song repeating "SPAM, SPAM, SPAM, SPAM... lovely SPAM! wonderful SPAM!", hence "SPAMming" the dialogue.
In the 1980s the term was adopted to describe certain abusive users who frequented BBSs and MUDs, who would repeat "SPAM" a huge number of times to scroll other users' text off the screen. In early Chat rooms services like PeopleLink and the early days of AOL, they actually flooded the screen with quotes from the Monty Python Spam sketch.
Sending an irritating, large, meaningless block of text in this way was called spamming.
This was used as a tactic by insiders of a group that wanted to drive newcomers out of the room so the usual conversation could continue. It was also used to prevent members of rival groups from chatting—for instance, Star Wars fans often invaded Star Trek chat rooms, filling the space with blocks of text until the Star Trek fans left. This act, previously called flooding or trashing, came to be known as spamming.
It later came to be used on Usenet to mean excessive multiple posting—the repeated posting of the same message."