hardening of the arteries

NOUN
25 LETTERS · STARTS WITH H

hardening of the arteries is a valid 25-letter word worth 33 points in Scrabble and 34 points in Words with Friends.

SCRABBLE WORDS WITH FRIENDS
H4A1R1D2E1N1I1N1G2O1F4T1H4E1A1R1T1E1R1I1E1S1
4 + 1 + 1 + 2 + 1 + 1 + 1 + 1 + 2 + 0 + 1 + 4 + 0 + 1 + 4 + 1 + 0 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 =33 PTS
DOUBLE WORD → 66TRIPLE WORD → 99
MEANING

What does hardening of the arteries mean?