Pronunciation: (rō'tu-siz"um), [key]
1. Historical Ling.a change of a speech sound, esp. (s), to (r), as in the change from Old Latin lases to Latin lares.
2. excessive use of the sound (r), its misarticulation, or the substitution of another sound for it.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.