As a deity name
Name 225 of the Vishnu Sahasranāma — Mahabharata (Anushasana Parva), as taught by Bhishma to Yudhishthira on his deathbed
As a Hindi name
विश्वात्मा · noun · masculine
विष्णु · शिव · ब्रह्मा — Śabdasāgara
विश्वात्मा · viśvātmā · s.m.
See s.v. وشوه viśva — Platts (1884), digital edition courtesy DSAL, University of Chicago, p. 1194
As a Sanskrit word
Meaning
the Soul of the Universe, the Universal Spirit, &c.
Scripturally attestedWhy this matches what you typed
M1 · same meaning "viśvātmā" is the nominative of "viśvātman" — the same word in a different grammatical case.
Dictionary citations
viśvātman m. the Soul of the Universe, the Universal Spirit, MaitrUp.; MBh.; Kum. &c.
the sun, L.
Caveats
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