Someone who is over a cup size C( which is the average cup size nationally) then they are considered big so that could be an example of big boobs.
But to other individuals, they consider big boobs to be artificial implants. It really depends on what type of individual you are but i hope these examples helped. :P
We can grow big breasts by doing sex with other boys because they suck our breasts.
BIG
as big as God intends
Big.
As Big as E
Big breasts are 'des gros seins' (familiar/slangish) in French.
Genetics.
It varies!
A cup
I guess that depends on how big your breasts are....?
Really big
How big are 44G breast