In addition to referring to pointless posts on the forums (see the wikipedia article ), as well as the canned meat product, the term "spam" in the context of OBD matches refers to a character repeatedly launching the same type of attack, thus "spamming" it. Attacks with a large charge - up time, which require special conditions, or which exhaust the user after one or a few uses, cannot be spammed. Physical attacks, such as punches, kicks, etc. are usually not referred to as being "spammed" even if they are launched in great number and rapid succession.
Attacks that are considered broken are often even more broken if they can be spammed. Spamming powerful attacks is usually out of character for many combatants, but if they have the capability to do so it is an acceptable tactic when bloodlust is in on. For example, The Culture would normally not resort to spamming gridfire in a war, especially not right off the bat, but they would if they were bloodlusted.