Can we get a site definition of what is 'Spam'?

It seems obvious right? But it's not. It is a slang term that has no hard definition. It gets used very differently by different people. I think most people more or less agree on the definition, but there are outliers who need it spelled out for them. By posting a definition in the TOS or elsewhere, it could shut-down some unintentional spamming, and also makes the trolling a bit harder. In past I have used this: "*Spam being defined as irrelevant posts, chronic reposting, or advertising*" But due to some extreme retardation in past, I would add "*Spam can take any form of message. Comments, posts, private messages, phone calls, smoke-signals, or other*".