Rhotacism
Pronunciation : Rho"ta*cism
Part of Speech : n.
Etymology : [Gr. "rwtaki`zein to use the letter r (r) overmuch: cf. F. rhotacisme.]
Definition : Defn: An oversounding, or a misuse, of the letter r; specifically (Phylol.), the tendency, exhibited in the Indo-European languages, to change s to r, as wese to were.
Source : Webster's Unabridged Dictionary, 1913