Microsoft Word knows more slang than you might expect. Words like zillion, jillion, squillion, gazillion, bazillion, and oodles are all recognized as correct spellings in Word’s US English dictionary, so you won’t get the dreaded red squiggly line if you drop one into a document. Word’s thesaurus even offers alternatives for “zillion,” though some of its suggestions (like million and billion) are precise numbers rather than true synonyms for an unspecified huge quantity.
There are many informal words to describe a non-specific but really large numbers. Word’s dictionary (at least in English) recognizes them as correct spellings.
If you want to be more specific see Real words for really big numbers in Microsoft Word
Zillion synonyms
Word’s thesaurus offers some alternatives to “zillion” though some aren’t really synonyms (million and billion are specific numbers).
Real words for really big numbers in Microsoft Word
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