Syllable division derived from spelling — this word is not in the pronouncing dictionary, so no phonetic transcription is shown rather than a guessed one.
unachievably is an adverb meaning "in an unattainable manner or to an unattainable degree". It carries one recorded sense.
in an unattainable manner or to an unattainable degree
“this house is unattainably expensive”
Definitions, synonyms and semantic relations for unachievably come from Princeton University’s WordNet. Commonness is measured against a corpus of everyday English. .