[rant mode]
Mostly this just grates on my nerves because it's a wrong use of the acronym.
MIRV stands for Multiple Independently targetable Reentry Vehicle. These are the submunitions of various classes of ICBM's and not the actual transport bus.
Where I see multiple posts about the use of "MIRV's", the actual subject being discussed is the transport bus with multiple submunitions. A better discription would be Multiple Warhead Missile, MWM for short.
I don't expect anyone to change thier terminology just because it bugs me. Just needed to rant.
[/rant mode]