An answer on Basic QSO format? mentions things like "QRM" and "QSB". What do those terms mean?
"QRM" is one of many Q-codes used as abbreviations in radio communication. "QRM" in particular refers to human-generated interference (as opposed to "QRN" which is used to refer to atmospheric noise). "QSB" refers to fading (variation in signal strength over time).
The codes originated from the desire to keep CW (morse code) transmissions as brief as possible due to the format's inherent bandwidth limits, but have stuck around and now often show up as abbreviations in regular conversation as well.