break
cascade
cataract
cheapening
chute
collapse
collapsing
comedown
crash
cut
debacle
deciduous
declension
declination
decline
declining
declivitous
decurrent
deflation
defluxion
depreciation
descendant
descending
descension
descent
devaluation
dive
down
down-reaching
downbend
downcome
downcoming
downcurve
downfall
downfalling
downflow
downgoing
downgrade
downhill
downpour
downrush
downsinking
downtrend
downturn
downward
downward trend
drooping
drop
dropping
fall