regressive sorites

18 LETTERS · STARTS WITH R

regressive sorites is a valid 18-letter word worth 21 points in Scrabble and 23 points in Words with Friends.

SCRABBLE WORDS WITH FRIENDS

R1E1G2R1E1S1S1I1V4E1S1O1R1I1T1E1S1

1 + 1 + 2 + 1 + 1 + 1 + 1 + 1 + 4 + 1 + 0 + 1 + 1 + 1 + 1 + 1 + 1 + 1 =21 PTS

DOUBLE WORD → 42TRIPLE WORD → 63

MEANING

What does regressive sorites mean?