Syllable division derived from spelling — this word is not in the pronouncing dictionary, so no phonetic transcription is shown rather than a guessed one.
sleeplessly is an adverb meaning "without sleep; in a sleepless manner". It carries one recorded sense.
without sleep; in a sleepless manner
“he was lying in bed sleeplessly”
Definitions, synonyms and semantic relations for sleeplessly come from Princeton University’s WordNet. Commonness is measured against a corpus of everyday English. Full sources and licences.