A combination of "boobs" and "tunnel vision" that hinders men from looking a well endowed woman in the face.
One group of women find this very irritating and assign all sorts of presumed motives to the man in question (especially if they're lesbians): "he's objectifying me", "I have a brain", "he doesn't take me seriously", "what a jerk", "stop gawking", etc. In protest, these women often remark "stop talking to my tits" or wear tight t-shirts (with an upward pointing arrow) that says "Hey! I'm up here." Whether the presumptions about these men are actually true depends on the man in question.
A second group of women understand that having a natural C cup, or larger, bust line (without being fat), is a blessing. (34 D is ideal of course). To these women, if the man with booblevision is a nice, decent, responsible guy, with a sense of humor (and could be introduced to their parents) then they are flattered to some degree. They know that this guy has an appreciation for their beauty in the same way that he appreciates: a Key West sunset, a polished red Ferrari, an otter playing in the wild, a perfectly thrown football, or even the Blue Angels executing an aerial fleur de lis.
A third group is not the least bit offended, because they are getting what they want. They use boobnosis and whatever "charm" they possess to try and overcome whatever they're lacking in physical attractiveness. In order to avoid the probability of contracting a myriad of STDs, some men will limit their sexual contact with this group to titty sex (use your imagination). These women are the diametric opposite of the first group.
And lastly, members of the Itty Bitty Titty Committee have rarely, if ever, personally experienced booblevision and so, ironically, may yearn to be occasionally objectified or gawked at. This attitude is the bane of feminism.
Roderick: "Yo Reggie, check out dat foo Leroy. He bees gotsin' da booblevision again."
Reggie: "Man, dat dude ain't no playa. He don't even wait 'till da ho' turn her head away to be peepin' at dem titties."