1) Abate 2) Abate as rainfall 3) Abate into a drizzle 4) Abatement 5) Back off 6) Back off a bit 7) Begin to subside 8) Break 9) Cease 10) Cessation 11) Diminish 12) Diminishment 13) Ease 14) Ease off 15) Give some slack 16) Go easier 17) Gradual reduction 18) Intermission 19) Interruption 20) Lessening of effort 1) Ease 2) Lull 3) Relief 
Letup is American slang for an interim.
[n] - a pause during which things are calm or activities are diminished
lull noun a pause during which things are calm or activities are diminished; `there was never a letup in the noise`