That stands for ElectroMagnetic Compatability. I run a lab that tests products to see if they meet the applicable requirements for emissions and immunity.

The rules can't cover everything! A electric drill and a TV set might both meet their respective requirements, but you're still going to get a seriously hashed-up picture if you plug them both into the same outlet.

The guitar manufacturers have been very slow to include effective EMI shielding in their products. Even custom made instruments that cost thousands of dollars arrive without good shielding in the control chambers, much less in the pickup pokets or the wiring channels.

I advise everyone to visit http://www.guitarnuts.com/ and take a look at their tips on how to improve the shielding of their guitars.