Zillion has 3 different meanings across 2 categories:
Noun
· Adjective
Noun
1
a very large indefinite number (usually hyperbole)
"there were millions of flies"
2
An unspecified large number (of); a gazillion.
"I've asked her to return my books a zillion times, yet she never seems to bring them back."
Adjective
1
very large indeterminate number
"a zillion people were there"
Broader Terms (hypernyms)