A female dog or an annoying and whiney female. A commination of "Beezy," "Biyatch" and "Bitch." I don't know why the R is in there, but...
If Paris Hilton and any girl (including Spencer) from the Hills combined their eggs and then took the sperm from Simon Cowell and had a threesome lovechild mess, that would be a great plot for a Hollywood SOAP. However, a breeznotch is just anyone who's a total bitch.