WordNet sense 1 (a very large indefinite number (usually hyperbole)):

billion, jillion, million, zillion

WordNet sense 2 (the number that is represented as a one followed by 18 zeros):

one million million million

WordNet sense 3 (the number that is represented as a one followed by 12 zeros):

one million million

WordNet sense 4 (being or denoting a numerical quantity but not order):

cardinal