If a reduction or increase is precipitous, it is fast or great (Cambridge)
very steep, high and often dangerous (Oxford)
بیوقوف ,احمق
Over the past 18 months, there has been a precipitous fall in car sales .(Cambridge).
A precipitous drop at the side of the road.(Oxford)
A precipitous fall
A precipitous drop
Abrupt
Sharp
Dizzying
Gradual
Calm
Precipitously