natural event

NOUN
13 LETTERS · STARTS WITH N

natural event is a valid 13-letter word worth 15 points in Scrabble and 20 points in Words with Friends.

SCRABBLE WORDS WITH FRIENDS
N1A1T1U1R1A1L1E1V4E1N1T1
1 + 1 + 1 + 1 + 1 + 1 + 1 + 0 + 1 + 4 + 1 + 1 + 1 =15 PTS
DOUBLE WORD → 30TRIPLE WORD → 45
MEANING

What does natural event mean?