Tracking

Generally used by military personnel to convey that they already understood something that was said to them.

Useful when you want to tell someone who's a higher rank than you that you already knew what they just told you, and you're kind of pissed that they thought you didn't already know, but the ridiculous stipulation of having to answer to a grown man who's only been in a year or two longer than you dictates that you can't have an opinion of your own, much less tell this man to piss off.

Disclaimer: is also used casually/non-aggressively, but its main appeal is that you can get away with being belligerent.

Corporal "Working Supervisor": Hey bitch, formation at 1600

Lance Corporal Second-NJP: Tracking.