It's the negation of the verb "to be". But it's BAD grammar. Examples: 1. It ain't too hard. (It isn't too hard) 2. She ain't going to the party. (She is not going to the party.) 3. They ain't old enough for this bar. (They aren't old enough for this bar.)

Es lo mismo que am not o are not dependiendo el pronombre, pero es muy informal...probablemente lo hayas visto en una canción

It's usually not good grammar, but it's very popular in music from 1960-ish and up, for example, "Aint that Peculiar" by Marvin Gaye https://www.youtube.com/watch?v=JaPl_mmmHnY and it's still used a lot in modern rap and pop. You don't usually use it in conversation unless you're quoting a song lyric when it's appropriate. For example, if you do something that seems tough, you might say "aint nothing but a G thang" (https://www.youtube.com/watch?v=flBuQ8ZZ7Bs) in a joking way.

First of all: If you're in a formal situation, don't use it. It's pretty terrible grammar. It basically means am not, are not, is not, etc.

Ooohh I love using this word. "Ain't nobody got time for that!" Ain't is a contraction for am not, is not, are not, has not, and have not.