"Long boobs" is a term which is used when one's boobs are long, not necessarily hanging, but just having an shape which have similar properties as a long object. It's important to take note that the term "Long boobs" only should be used in occasions where it is used as a compliment.
"Swanoogle my broogle, you have long boobs today. Nice!"
"W'up bro, yo ma nig' yo tit' ies r pret'ty darn long to'day my brodda."
"Long boobs!"