Sehr interessant! Nachdem ich alle Antworten oben durchgelesen habe, habe ich die meines Erachtens drei besten Beiträge zusammengefasst:
a) sexuelle Avance am Telefon, die fast ausschließlich erst spät nachts und oft nach einer Party, einem Kneipentour oder jedenfalls ein paar Bierchen versucht wird
"Alright man, time to place the booty call."
"Girl, I just got a/the booty call."
b) der nicht-dominantere von beiden Beteiligten, der den Anruf bekommen hatte
"Nah, we're not dating, she's just my booty call."
"You know he's just using you for a booty call!"
Like all words in the English language, especially American slang, the meaning varies with the context of its use. The term popped up once young adults, especially high school and college students, started using cell phones in the late 90s. At that point it became very easy for them to arrange late-night rendezvous after a night of drinking (because the number one reason all Americans go out to a party or bar is to either have a one-night-stand or meet a significant other). Like most American slang, its roots are in African American English (See the 1997 film "Booty Call"), where it has long since been popularized by Hollywood and the music industry and spread to even old, rich, white men.
A booty call always implies person A calling person B to arrange for a sexual encounter. Usually, one of the involved parties goes to the other's place of residence to do the deed. And it very frequently involves alcohol before placing the call or accepting the call. But a booty call is just the actual placing of a call for the purpose of sex. It is not the act of sex itself.
A booty-call is not the same thing as a "quickie". A quickie implies either a limited amount of time and/or an unconventional location, both of which require doing the deed very quickly. A booty-call can entail a quickie or an all-niter. :) The "guest" can leave (or be kicked out) immediately after the deed, or can spend the night. A quickie also implies doing it just once in a specified (short) amount of time. But depending on the people, a booty call can result in a series of quickies and/or "longies". :)
A booty call is also not the same thing as a "one night stand". A one night stand is self explanatory: you do it once, often regret it, and never do it again, even if one or both kinda want to. A booty call can definitely result in a one night stand. But what usually happens is the caller realizes it worked the first time, and keeps calling back periodically or even regularly until it stops working. :) The goal of a booty call is sex without any commitments or investments in a relationship (as if that is humanly possible... booty callers still get jealous!), and a lot of people who lace boot calls have a list of numbers and people they go down when all else fails. That is the crucial aspect. A booty call is often a back-up plan, even a last resort. You went out to a party or bar, hoping to meet someone, and when you went home alone, you went down your list of numbers until you got a positive response. But I have heard pairs in seriously relationships jokingly refer to their boyfriends or girlfriends calling late at night for sex as a "booty call". I have also known of many informal/open relationships between friends and acquaintances that essentially amounted to a long history of booty calls...
There are also sociocultural phenomena to consider. It is typically the guy (or the more dominant person in a relationship) that places the booty call. And like all things regarding sex, it is typically considered positive if a guy gets a booty call from a girl (he brags about it) and negative if a girl gets one (she is often embarrassed by it and hides it). This of course depends on both the individual and the dynamic between the two parties. Though I have never met a guy embarrassed about a booty call, because they even brag if they find the female caller repulsive (they only hide the fact that they actually agreed to the proposition! :) ), I have known girls who brag and openly talk about their booty calls. And even girls place booty calls!!
Another facet: I once got a booty call via AOL Instant Messenger. And since I graduated college before text messaging got big, I can only wonder what goes on now. There has to be a new word: "Booty texting" or something...
Interesting and important concept! Definitely one that any foreigner studying, probably even working, in the US needs to grasp!! I know for a fact that the same thing happens in Germany... I just never encountered a specific word for it. Maybe because we are so open about this phenomenon and because it is so pervasive in our popular culture...