Syllable division derived from spelling — this word is not in the pronouncing dictionary, so no phonetic transcription is shown rather than a guessed one.
unimpressively is an adverb meaning "in an unimpressive manner". It carries one recorded sense.
in an unimpressive manner
“she scored unimpressively low in the first round of the competition”
Definitions, synonyms and semantic relations for unimpressively come from Princeton University’s WordNet. Commonness is measured against a corpus of everyday English. .