Both Uses

Hinduism
in
Main Street, by Sinclair Lewis
(Auto-generated)

And by the chance of propinquity she read scores of books unnatural to her gay white littleness: volumes of anthropology with ditches of foot-notes filled with heaps of small dusty type, Parisian imagistes, Hindu recipes for curry, voyages to the Solomon Isles, theosophy with modern American improvements, treatises upon success in the real-estate business.†
Chpt 1

Hindu = someone who believes in Hinduism (the third most common religion--which has many gods and is associated with India)
For every housewife and every longshoreman and every Hindu nationalist and every teacher.†
Chpt 16 *

Definitions:

(1) (Hinduism)
the third most common religion; polytheistic (many gods) with most adherents in India

Only Christianity and Islam have more followers than Hinduism.
(2) (meaning too rare to warrant focus)