Top Definition
MFDD is a military slang term for a potentially apocalyptic device and it stands for..."MOTHER F@$#ING DOOMSDAY DEVICE."
"Noble 6" threw an "mfdd" into a covenant ship and blew it all to hell. In case you didn't know, that was a reference to the video game HALO REACH.
by DykesVespar September 07, 2010

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