25
sincerely(adverb, manner, sincere, politeness, artlessly)
16
earnestly(adverb, fast, resolution, intensely, fiercely)
14
severely(adverb, fast, badly, completely, intensely)
14
gravely(adverb, badly, severely, completely, poorly)
10
soberly(adverb, sincerely)
9
badly(adverb, poorly, strictly, harshly, sternly)
9
intensely(adverb, fast, badly, severely, thoroughly)
8
in all conscience(expression, idiom, adverb, greatness, really)
7
critically(adverb, badly, strictly, harshly, sternly)
7
dangerously(adverb, badly, strictly, harshly, sternly)
7
in earnest(expression, idiom, adverb, resolution, affirmation)
7
solemnly(adverb, earnestly, truly, sincerely, grimly)
7
thoughtfully(adverb, intensely, earnestly, actively, truly)
6
grimly
6
really
6
truly(adverb, greatness, affirmation)
5
fervently(adverb, thoroughly, vigorously, earnestly, actively)
4
acutely(adverb, badly, severely, thoroughly, completely)
4
decidedly(adverb, greatness)
4
deeply
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APASmart Define. (2016). seriously thesaurus. Retrieved September 22, 2026, from https://smartdefine.org/seriously/thesaurus/synonyms
ChicagoSmart Define. 2016. "seriously thesaurus" https://smartdefine.org/seriously/thesaurus/synonyms (accessed September 22, 2026).
HarvardSmart Define 2016, seriously thesaurus, Smart Define, viewed 22 September, 2026, <https://smartdefine.org/seriously/thesaurus/synonyms>.
MLASmart Define. "seriously thesaurus" 31 March 2016. Web. 22 September 2026. <https://smartdefine.org/seriously/thesaurus/synonyms>