When terms with multiple, differing meanings conflict in a given context. A portmanteau of "nomenclature" and "clash". Especially useful for abbreviations like "BPM" when there's a doctor, a DJ, and a network technician in the same room.
It will be a huge nomenclash if we name our new line of scents for pilots "May-day". I know nomenclashes abound when it comes to airline jargon, but you have to find a better name.