Quad- Vocabulary: Crossword Puzzle

Double an amount that is already doubled.
You do this when you cut an apple into four, equal portions.
An example of this is the Empire State Building.
Shapes with only four angles.
Leap years are this.
90 degrees of a complete circle.
Most polyglots can be described by this adjective.
You'll be a rapid runner if you work these out.
Four of the same item.
An animal that has two more feet to walk on than humans do.