This is an expression used by Brazilian
children to describe
that they don't know how to define. For example,
some complicated compound of green
with a hint of orange
I don't know of any equivalent expression in English.
This was told to me by a friend of mine from Rio de Janeiro, so
it must be true. He didn't say whether
the ass in question is of the donkey
or arse variety, but I'm presuming the former.