Extra letters or phases inserted into a real email address to prevent an address harvester from using it. The extra ballast should be easy for a person to spot, but difficult for even a smart address harvester to deal with.

It's useful when posting on newsgroups, bulletin boards of any sort, or web pages.

"markwilliamforest@deadseagull.com" could become "markSPAMwilliamMONGERINGforest@deadseagullsBASTARDS.com"

Of course, spam armor is only necessary when you actually need a response. At all other times, use "admin@real.com"