An avenue with a long official name, for example, Mass-av (instead of Massachusetts Avenue) and Comm-av (rather than Commonwealth Avenue). For many years, the Boston Globe even used "av." (yes, in lower case) rather than "Ave."
My wife once got mad at me for calling avenues here in Ohio _________ AV! She told me, it's not AV but AVENUE. I told her, well it's not POP either it's SODA or TONIC. Grr..the midwest :( I miss Boston!
I STILL hear it!
Wow, I've lived in a small city North of Boston all my life, and I had no idea that people out of the area didn't say av! I've traveled around the US a lot, and I never noticed it... until now.