belch
burst
cascade
cataract
chute
collapse
comedown
crash
debacle
debouchment
declension
declination
defluxion
descending
descension
descent
dissiliency
down
downbend
downcome
downcurve
downfall
downflow
downgrade
downpour
downrush
downtrend
downturn
downward trend
drop
dropping
eructation
eruption
fall
falling
flare-up
gravitation
gush
inclination
jet
outbreak
outburst
plummeting
pounce
rapid
riff
riffle
ripple
rush
sault