Originated on behalf of a certain anti-chav site, used to describe the odd relationship apparently inbred chavs have with other (female) members of their family.
Like it's male counterpart bruncledad, it derives from sister, aunty, and mum, with those terms being the female form of the words that make up the term bruncledad.
Again, with this defenition, no-one has been able to figure out how it is possible for a single female relative to be all of these things at the same time to the same person.
Whether or not this will become a suitably humourous counterpart to the word bruncledad is yet to be decided.
It is also worth noting that the word sounds a lot like chrysanthemum.
He's just received his first giro. His sisauntymum must be so proud.
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