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 shoot spate spew spurt stoop swoop torrent volcan waterfall