ACMS
Yep, I think it's also know as co-channel interference. It's not so much deliberate jamming or deliberate interrogation, it's just RF energy from another source entering your radar system when it is "listening" for it's own return.
There seems to be a persistant source "jammer" for the 744 wx radar to the South of the Maastrict sector....never been able to find it's source but it's often there.