Used by investment bankers(usually analysts) to mean they have something to get done and get back to someone really fast. Part of speech is variable. Also used by bankers when they go out to mean chug your drink.
"No, I'm firedrill right now for a VP"
"Oh that sucks, I had a bunch of firedrills this morning"
"I hate being in firedrill mode"
"Yeah I wish we hadn't firedrilled those shots last night"
when you suddenly need to use the bathroom.
*while doing squats at practice* "FIREDRILL!!!!"