Short for Ballistic Missile Defense Office. A part of the Pentagon
WARNING: RANT FOLLOWS!
A bunch of completely venal frauds attempting to waste the maximal part of our (U.S. citizens') tax dollars by pissing away billions upon billions on a system that manages to fail even those tests they admit to having rigged. Even if they ever got it to work, it will cause the abrogation of the ABM Treaty, one of the few arms-control agreements with a history of working and working well, and completely piss off the Russians and Chinese (with good reason). Cited as a defense against 'rogue states', this completely ignores the fact that ballistic missiles are in fact one of the most difficult means imaginable to deliver a nuclear warhead. This is especially true given how far the U.S. is from these so-called rogue states.
In addition, even if the thing might ever work in practice conditions (what a professor of mine refers to as hitting a strapdown chicken) the countermeasures that might be taken to defeat it are all extremely easy and cheap to implement, especially compared with the effort of building a working IRBM or ICBM in the first place! Mylar balloons with metal coatings to confuse radar (put the warhead itself inside one, even; it'll look identical to the others), gas cooling of the ballistic shell to confuse IR seekers, asymmetric shells to MARV the warhead for no additional cost and an accuracy penalty that's irrelevant if the missile is a countervalue strike: all of these would render even a perfectly working version of the system that the BMDO describes to us useless.
If the BMDO was serious about treating this as a threat instead of a budgetary boondoggle, they would spend more time investigating those methods of missile defense that physics says are easier, such as boost-phase intercept; working on those time periods of the missile flight where physics are in your favor (and, incidentally, not voiding the ABM treaty). But instead, they continue to pour money into an interceptor-based terminal defense that DOESN"T FSCKING WORK, rig tests, classify studies that aren't in their favor while deriding them as inadequately informed, and invoke bullshit cliches like 'peace shield' and 'the insanity of MAD.' This completely ignores the fact that deterrence has worked for the last fifty years, even under extremely trying conditions!