quadrupling >> /ˈkwɒdrʊp(ə)l/
Definition: [verb] Increase or be increased fourfold.
Example: oil prices quadrupled in the 1970s
Definition: [noun] A quadruple number or amount.
Example: Now that marriage no longer means much, why not let couples or triples or quadruples of whatever variety get married?
Definition: [adjective] Consisting of four parts or elements.
Example: a quadruple murder