A noticeable deterioration in performance or quality:
— A drop-off in attendance.

synoniemen: falling off, falloff, slack, slump.

A steep high face of rock.

synoniemen: cliff, drop.

Nederlands: klif, klip
Pools: klif, faleza

A change downward:
— There was a sharp drop-off in sales.

synoniemen: decrease, lessening.

Nederlands: terugloop
Pools: zmniejszenie się, zmalenie, pomniejszenie się