lessening

NOUN
9 LETTERS · STARTS WITH L

lessening is a valid 9-letter word worth 10 points in Scrabble and 14 points in Words with Friends.

SCRABBLE WORDS WITH FRIENDS
L1E1S1S1E1N1I1N1G2
1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 2 =10 PTS
DOUBLE WORD → 20TRIPLE WORD → 30
MEANING

What does lessening mean?