This fascinating article sent me back to Q to review all the D5 drops.
I hereby withdraw any comments I have made before on this topic, because I don’t think it has been decoded yet.
This missile does not fit; nor does the earthquake theory; nor the D5 = 45 theory etc.
I am imagining it will be revealed (i.e., proved) in the future—perhaps when the additional 20 pages of FISA are revealed ... perhaps some other time.
I have believed from the first D5 that is refers to an avalanche. It fits for every time it has been used.