Syllable division derived from spelling — this word is not in the pronouncing dictionary, so no phonetic transcription is shown rather than a guessed one.
heedlessly is an adverb meaning "without care or concern". It carries one recorded sense.
without care or concern
“carelessly raised the children's hopes without thinking of their possible disappointment”
Definitions, synonyms and semantic relations for heedlessly come from Princeton University’s WordNet. Commonness is measured against a corpus of everyday English. .