linear measure

NOUN /lɪniər_'mɛʒər/
14 LETTERS · 4 SYLLABLES · STARTS WITH L

linear measure is a valid 14-letter word worth 15 points in Scrabble and 19 points in Words with Friends.

SCRABBLE WORDS WITH FRIENDS
L1I1N1E1A1R1M3E1A1S1U1R1E1
1 + 1 + 1 + 1 + 1 + 1 + 0 + 3 + 1 + 1 + 1 + 1 + 1 + 1 =15 PTS
DOUBLE WORD → 30TRIPLE WORD → 45
MEANING

What does linear measure mean?