Somewhat of a derogatory term which stands for "American Born Confused Desi" and usually refers to an Indian born and raised in the United States.
Traditionally, the ABCD has been known to have abandoned his roots, so to speak, refusing to watch Bollywood films, listen to Indian music, participate in Indian social functions, etc, as a previous definition states. He will even go so far as to pretend that he is areligious. Indeed, the "ABCD", somehow considers himself superior to native Indians (not Native Americans) or immigrant Indians simply for the fact that he (or she) was not born in the homeland. In their mind they are "American", whatever that means to them.
The truth of the matter, however, is that the "ABCDs" could not be farther from "American", as they often have no clue what it is to actually be "American". They have no sense of culture (their own, or "American"), history, or any awareness of the world beyond their own, which consists of hanging out with other ABCD's, who are equally proud to not have been born in the homeland. As the previous definition states, ABCD's rarely if ever hang out with non-desis, even though they may strive to someday. For all their hatred for everything desi, it is almost ironic that it is the desi who they exclusively hang out with, and probably wouldn't be able to survive without.
It is true that ABCD's are usually pre-med, following the urging of their parents. This is the mark of an ABCD - he/she tries to give the impression of being independent thinking as well as "American", but in the end just ends up choosing the medical (or related) career their Indian parents told them to since the age of 2 months.
As far as other things go like drinking habits, well the ABCD considers drinking alcohol a "cool" and "American" activity, and will readily engage in it. They often overdo it, and this is no surprise because they are known to try too hard to be "American" or "white". Their actions are quite humorous to an observing third party and perhaps they make bigger asses out of themselves than FOBs, who also have issues regarding their identity. They, too, act retarded when trying too hard to assimilate, but we will leave that discussion for another day.
In sum, the ABCD is uncomfortable in his own skin, cannot be himself, and generally suffers from an identity crisis. They are frauds who simply act rather than just living life and being themselves. They are caught up with everything in this world that is superficial. In this regard, they perhaps are bigger idiots than FOBs, who interestingly are the ABCD's main target for ridicule.
There are several other things worth noting about the ABCD. For example the female ABCD seems to think that rap/hip-hop music is the way and the only way to prove her "American-ness". Thus, she will brag to whoever listens that she is a huge fan of it. She will also go for the orange highlights in her hair, because the pure black thing is way too "desi" for her. She chooses to look like a Hispanic instead. To her, being Latino is apparently more "American". As for the desi male..well he will often try his hardest to act "gangsta" only to look like a complete and utter imbecile. But so long as he is chillin with other desi wannabe gangstas (aka wimp ass morons), what he doesn't know won't hurt him. Perhaps, though, if he ever looked in the mirror, he would realize that the short, spiked, and geled up hair (with the long, thin sideburns) on the dark brown skin looks utterly ridiculous.
The best advice that an ABCD, and likewise a FOB, can use is: "Just be yourself".
"Look at DJ Vinod trying to call himself DJ Vinny. Man what an ABCD."
"Oh so you don't like samosas anymore is that it? Go choke on some pasta you damn ABCD."
Vikram, the ABCD, declared his disgust for anything related to being Indian. Unfortunately he was spotted several times at Indian grocery stores, and eventually ended up becomming a pharmacist.