You'll have to see Bush Mama to learn the significance of the title. For one thing, the film isn't set in Australia or Africa. It takes place in the black ghetto of LA, where a welfare mother struggles to raise her daughter. The mother has a checkered past, as we learn during several unsettling flashback sequences.
Throughout Bush Mama, graphic violence rubs shoulders with flights of fantasy; the contrast is fascinating, even when it doesn't quite work dramatically.