QRM is also used as a noun
, in which case it means "interference from other stations". If an radio amateur
says: "I got his callsign
all right, but after that, I lost him in the QRM", he means that one or more stations started sending on the same frequency that he was using, thus making him unable to hear the station he was conversing with.
Radio amateurs metaphor even use "QRM" for non-radio kinds of interference. Thus, it's not uncommon to hear hams talking to each other in crowded places complain about having difficulties because of the QRM.