'zillion' definitions:

Definition of 'zillion'

(from WordNet)
adjective
Very large indeterminate number; "a zillion people were there"
noun
A very large indefinite number (usually hyperbole); "there were millions of flies" [syn: million, billion, trillion, zillion, jillion, gazillion]

Synonyms of 'zillion'

From: Moby Thesaurus