Internet boobs are boobs that are so breathtaking that you would find them on a porn site. Of course it is difficult to find someone with internet boobs in real life, which is what makes it all the more special. Note that they are not enormous boobs but boobs that take all the necessities like proportion into account.
"Holy shit, did you see her?" (stunned silence) "I just did." "That was the chest of a goddess." "Indeed. Internet boobs."