Is there an "ain't"?
Does Spanish have a catch-all slang word as useful as the English slang word "ain't" ?
4 Answers
I've never heard any such word in Spanish, but we do shorten words a lot
I think what Billy Jones is referring to is not so much the shortening of words as much as the fact that ain't is not a shortening of a single pair of words, but encompasses several sets (tenses, person etc).
Where people use this word, the word can be used as a contraction of all of the following (note that all of these are colloquial usages and would not be correct in an academic setting):
1). Is not - He ain't the person I'm looking for
2). am not - I ain't here to bargain with you
3). have not - I ain't come here to bargain with you
4). are not - You ain't the one I'm looking for
5). has not - He ain't been here long
6). did not - I ain't have any money
7). do not - I ain't got any money (this extremely colloquial)
This is what Billy means by catch-all slang word because it is used across tenses and person. The only thing that I would point out is that this is not so much a slang word as it is a colloquialism that is extremely prevalent across the southern United States and probably as ubiquitous as the southern contraction y'all (but that's another topic).
This posting is primarily to help those who are learning English
AIN’T = AM NOT, ISN’T, AREN’T, HAVEN’T
“Ain’t” has a long and vital history as a substitute for “isn’t,” “aren’t” and so on. It was originally formed from a contraction of “am not” and is still commonly used in that sense. Even though it has been universally condemned as the classic “mistake” in English, everyone uses it occasionally as part of a joking phrase or to convey a down-to-earth quality. But if you always use it instead of the more “proper” contractions you’re sure to be branded as uneducated. What ever is said about the word “ ain’t “ it ain’t pretty English. It is ugly English. Ain’t is not a verb. It can only be used in the present tense.
All learners of English as a second language need to understand what it can mean but they should also try not to use it. It never needs to be used; there is always another way of saying the same thing.
Ain’t is a contraction. Other contractions include: I’m I’d he’s he’d can’t shouldn’t haven’t isn’t etc
The difference between ain’t and the other contractions is that ain’t is not normal. (“ain’t” ain’t normal) Ain’t can be a contraction of several origins.
For example:
I’m is a contraction of I am
He’s is a contraction of he is
Can’t is a contraction of can not a.s.o.
But
I ain’t can be
I am not = I ain’t happy. I am not happy.
He ain’t can be
He is not = He ain’t happy. He is not happy.
But
I ain’t can also be
I have not got = I ain’t got no money. I have not got any money.
He ain’t got can also be
He has not got = He ain’t got no money. He does not have any money.
We ain’t got can be
We do not have = We ain’t got no money. We don’t have any money.
Notice that ain't is sometimes used where it makes a double negative "I ain't got no money" Double negatives are a "no no" in correct English
Ain’t is always ain’t - for all persons
I ain’t
you ain’t
he ain’t
she ain’t
we ain’t
they ain’t
I ain’t going to the party. I ain’t got no information. You ain’t my brother. You ain’t got any brothers or sisters. You ain’t got no brothers or sisters. He ain’t here. He ain’t got no time for sport. She ain’t pretty. She ain’t got no make-up. We ain’t coming until tomorrow. We ain’t got time for nothing. They ain’t very funny. They ain’t got no talent.
No, de lo que yo sé. No, not that I know of. Then again, I don't really know much "slang"! 
I've never heard any such word in Spanish, but we do shorten words a lot.
For example when we say:
¿Para que tu quieres ir? --- Why do you want to go? --- sometimes we say --- ¿Pa' que tu quieres ir?
No me importa nada --- I don't care about anything --- we can say: No me importa na'
We have a lot of phrases like this but you don't need to know them now. They will just make you confuse.
