A kangaroo is a large animal that leaps or springs on its big, strong back legs and uses its heavy tail for balance. If you visit Australia (or the zoo), you may see a kangaroo.
Kangaroos are known for their habits of sitting upright and springing great distances. Female kangaroos have pouches in which they carry their babies. The word kangaroo is thought to come from a now-extinct Aboriginal language's word for a specific kind of kangaroo, gaNurru or gang-oo-roo. A "kangaroo court" is one that operates outside of the law, often with the intention of quickly (and unjustly) trying someone for a crime.