royal line

NOUN
10 LETTERS · STARTS WITH R

royal line is a valid 10-letter word worth 12 points in Scrabble and 14 points in Words with Friends.

SCRABBLE WORDS WITH FRIENDS
R1O1Y4A1L1L1I1N1E1
1 + 1 + 4 + 1 + 1 + 0 + 1 + 1 + 1 + 1 =12 PTS
DOUBLE WORD → 24TRIPLE WORD → 36
MEANING

What does royal line mean?