1. When someone has asked you to do something for them, in which you agreed to do it, but then you forget to.
2. When you borrow something then lose or break it and dont tell the borrower, then they ask about it.
3. When you owe someone then you don't have their money.

In support of.

when someone says an unfunny joke which is then followed by silence. so to break the silence you say "about that".

Used in slang especially in Britain, in place of "No Way" or "Bullshit"
The way it works is that it negates the following sentence, much in the way the above examples would. used in street slang and grime music

To mention about something else that is on top

Usually used in a Derogatory nature what ever word follows now means the opposite of what it meant before. Can also be pronounced “bout”

A phrase used by North Carolinians describing something they don't like or don't want to do. Synonym for no.

can either be a verb (to be about it) or a command (be about it). means that the person is not scared and is ready to do the act, whatever it is

All around; on every side
The construction not about to is often used to express determination: We are not about to negotiate with terrorists. A majority of the Usage Panel considers this usage acceptable in speech but not in formal writing. ·About is traditionally used to refer to the relation between a narrative and its subject: a book about Cézanne; a movie about the Boston Massacre. This use has lately been extended to refer to the relation between various nonlinguistic entities and the things they make manifest, as in The party was mostly about showing off their new offices or His designs are about the use of rough-textured materials. This practice probably originates with the expression That's what it's all about, but it remains controversial. Fifty-nine percent of the Usage Panel rejected this use in the example A designer teapot isn't about making tea; it is about letting people know that you have a hundred dollars to spend on a teapot.