Synonyms for Lessening:

adj.

lessening (adjective)
shrinking, fading away, wearing down, dwindling, declining, depreciating, wasting, Quieting, wearing off, softening, moderating, dying down, narrowing, lowering, slackening, slowing, ebbing, diminishing, dropping, waning, sinking, shriveling up, sagging, Slumping, plummeting, losing momentum, abating, weakening, subsiding, Plunging, lightening.

n.

abridgement (noun)
cutting, curtailment, reducing, Diminishment.
appeasement (noun)
soothing, easing.
contraction (noun)
Abridging, decreasing, Curtailing, elision, shrinking, receding, condensing, deflating, Abbreviating.
decrement (noun)
subtraction.
deterioration (noun)
Decaying, depreciation.
lessening (noun)
decreasing, decrease, reduction, drop off.
shortening (noun)
narrowing.
subtraction (noun)
depreciation, elision, decrease, abridgement, subtraction, deletion, reduction, deduction, Diminishment, curtailment.

v.

alleviating (verb)
Mitigating, moderating, Palliating, soothing, Alleviating, Allaying, easing, Relieving, Assuaging.
decreasing (verb)
Truncating, abating, eroding, shrinking, receding, Deducting, decrementing, dwindling, deflating, draining, Compacting, Abbreviating, Curtailing, dying down, contracting, Abridging, Concentrating, Depleting, subsiding, shortening, diminishing, lowering, decreasing, compressing.
detracting (verb)
Derogating, Detracting, Abrading, depreciating, Maligning, Defaming, Discounting, Decrying, casting aspersion, disparaging.
diminishing (verb)
shaving, downgrading, minimizing, Bobbing, pruning, clipping, nipping, tapering, condensing, Cropping, trimming, lightening, reducing, Weeding, Culling, shearing, paring.
lessen (verb)
decrease.
lightening (verb)
unloading.
shortening (verb)
narrowing.
subtracting (verb)
docking, cutting, Subtracting, Deleting, Eliding.

Other synonyms:

drop-off
drop off.
Other relevant words:
slackening, narrowing, softening, waning, slowing, weakening, sagging, sinking, dropping, wasting, Quieting, Decaying, declining, Slumping, plummeting, ebbing, Plunging, drooping.

Usage examples for lessening

  1. The drag on the wire was lessening the speed of his machine now and jerking dangerously at intervals. – Tom Slade Motorcycle Dispatch Bearer by Percy Keese Fitzhugh
  2. The corporations are like stitches that form a net, holding together through community of interests and a general desire for prosperity, yet each having its own separate formation and the power to enlarge itself and increase its activities without compromising the others or lessening their respective importance. – Modern Saints and Seers by Jean Finot