planetary precession

20 LETTERS · STARTS WITH P

planetary precession is a valid 20-letter word worth 28 points in Scrabble and 33 points in Words with Friends.

SCRABBLE WORDS WITH FRIENDS

P3L1A1N1E1T1A1R1Y4P3R1E1C3E1S1S1I1O1N1

3 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 4 + 0 + 3 + 1 + 1 + 3 + 1 + 1 + 1 + 1 + 1 + 1 =28 PTS

DOUBLE WORD → 56TRIPLE WORD → 84

MEANING

What does planetary precession mean?