* OED: https://www.lexico.com/en/definition/om
* AHD: https://www.ahdictionary.com/word/search.html?q=om
* Collins: https://www.collinsdictionary.com/dictionary/english/om
* MW: https://www.merriam-webster.com/dictionary/om

"Variant of om":
* https://www.merriam-webster.com/dictionary/aum
* https://www.ahdictionary.com/word/search.html?q=Aum

English dictionaries prefer "om". Please also align the x-ref.

@@ -13,2 +13,2 @@
-<gloss>aum (ritual chant in Hinduism, etc.)</gloss>
-<gloss>om</gloss>
+<gloss>om (ritual chant in Hinduism, etc.)</gloss>
+<gloss>aum</gloss>

OK. Since most of the discussion of this term in Japanese uses "オーム" we'd better have that as an entry too.

@@ -11,0 +12 @@
+<xref type="see" seq="2848293">オーム</xref>

daijr koj nikk
all just have 唵 おん
https://ja.wikipedia.org/wiki/オーム_(聖音)
wiki doesn't suggest 唵 can be read オーム either.

daijr says [感]

We don't usually tag 音写 and we usually don't use katakana for them. I'm not seeing a strong case for オウム being read 唵 - 
it's not in any of the kokugos and I don't think the 新英和大辞典 is necessarily saying it's read that way either?

koj and daijr mention its used in mikkyo. It's a little weird to suggest that 唵[おん] is used by Hinduists when that's most 
likely not the case - even in Japanese, I'd assume they say オウム rather than おん. but I'm speculating.

unclear if uk or not.

@@ -8,4 +8 @@
-<reb>オーム</reb>
-</r_ele>
-<r_ele>
-<reb>オン</reb>
+<reb>おん</reb>
@@ -14,3 +11 @@
-<pos>&n;</pos>
-<misc>&uk;</misc>
-<lsource xml:lang="san"/>
+<pos>&int;</pos>

The explanation in Daijisen begins: "《〈梵〉oṃの音写》インドの宗教や哲学で、神聖で神秘的な意味をもつとされる語。" before going on to the "仏教でも...". It's primarily used in Hindu and related contexts, and from there it leaked into Tibetan Buddhism. I don't think it's primarily a Buddhist term which is why I dropped the tag.
唵 is really an ateji, assigned to the syllable in China because it sort-of matched the sound. Its precise readings in Japanese, where it's a very rare kanji, are not that relevant to this word.

@@ -15,0 +16 @@
+<lsource xml:lang="san"/>