In a manner that shines brightly or radiates brilliantly; with dazzling radiance or luminosity.
Adverbial form of the adjective 'effulgent' (shining brightly), formed by adding the suffix '-ly' to create a modifier describing how something shines or appears.
It's fascinating that English borrowed heavily from Latin for abstract scientific and poetic language—'effulgently' sounds rarified and special partly because most English speakers learn simple 'bright' first and never encounter these Latin-rooted alternatives.
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