What does "person" mean in US Constitution?

That really is more of a law question than a history question.  On matters of Constitutional interpretation I suggest that you consult with organizations such as Cornell Law School's Legal Information Institute.

Dear Mr. Bruno,

Thanks for posting your request on History Hub!

We suggest that you search for related information about the term “We the People” at the following web sites:

https://www.archives.gov/founding-docs/constitution;

https://constitutioncenter.org/interactive-constitution/preamble’; and https://www.annenbergclassroom.org/constitution/

We hope this is helpful. Best of luck with your research!