Syllable division derived from spelling — this word is not in the pronouncing dictionary, so no phonetic transcription is shown rather than a guessed one.
fastidiously is an adverb meaning "in a fastidious and painstaking manner". It carries 2 recorded senses.
in a fastidious and painstaking manner
“it is almost a waste of time painstakingly to learn the routines of selling”
in a fastidious manner
“he writes extremely musical music, of which the sound is fastidiously calculated and yet agreeably spontaneous and imaginative”
Definitions, synonyms and semantic relations for fastidiously come from Princeton University’s WordNet. Commonness is measured against a corpus of everyday English. Full sources and licences.