intersubstitution

17 LETTERS · 6 SYLLABLES · STARTS WITH I

intersubstitution is a valid 17-letter word worth 19 points in Scrabble and 24 points in Words with Friends.

SCRABBLE WORDS WITH FRIENDS

I1N1T1E1R1S1U1B3S1T1I1T1U1T1I1O1N1

1 + 1 + 1 + 1 + 1 + 1 + 1 + 3 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 =19 PTS

DOUBLE WORD → 38TRIPLE WORD → 57

MEANING

What does intersubstitution mean?