verb. ['kwɑːˈdruːpəl'] increase fourfold.
noun. ['kwɑːˈdruːpəl'] a quantity that is four times as great as another.
adjective. ['kwɑːˈdruːpəl'] four times as great or many.
noun. ['kwɑːˈdruːpəl'] a set of four similar things considered as a unit.
adjective. ['kwɑːˈdruːpəl'] having four units or components.