betacism

noun2

1. •
   A sound change in which [b] (the voiced bilabial plosive) shifts to [v] (the voiced labiodental fricative).

   • Betacism is a fairly common phenomenon: it has taken place in Greek, Hebrew, Spanish, and some Portuguese dialects, among others.
2. •
   A speech disorder involving excessive use of the [b] sound, or conversion of other sounds into it.