its a hybrid of
ridonkulous (extremly ridiculous) a badonkadonk (a huge
ass in comparison with a womens body)
In other words its a ridiculusly huge
ass
ridonkulous + badonkadonk = ridonkabonkadonkulous
Alfie : damn! that girl has badonkadonk !
James : thats a ridonkulous badonkadonk!
Roger & Harry :NO U HO-MO-
FOS! that girl is ridonkabonkadonkulous!