"NCO" (Non-commissioned officer)
"WO" (Warrant Officer)
Military terms. I was trading some with a guy today who's learning them. He knew the above.
"Stand-down." This former brat remembers these: my dad would come home early some summer days because it was too hot to work. "We had a stand-down."
"MP" (Hint: these guys and girls show up for work -- unlike Ottawa MPs.)