In article ,
Tman wrote:

What is that -- and does it matter to GA avionics? Heard it referenced
a few times in the sale of an older GIII. But Google does not turn up much.

(It's not applicable in the USA.)

It has to do with the lack of frequency protection for ILS. High
power FM stations (in Europe) can bleed enough RF into ILS frequencies
that ILS receivers (and technically VOR receivers) need to do a
better job rejecting out-of-channel frequencies.

I can dig up some references from work, but I'm not sure
how many are available for free.