Syllable division derived from spelling — this word is not in the pronouncing dictionary, so no phonetic transcription is shown rather than a guessed one.
sleeplessness is a noun meaning "a temporary state in which you are unable (or unwilling) to sleep". It carries one recorded sense.
a temporary state in which you are unable (or unwilling) to sleep
“accept your wakefulness and sleep in its own contrary way is more likely to come”
Forms marked · are formed by the regular rule rather than recorded in the source data. English keeps a few hundred irregulars and the rest follow the pattern, so the rule is right far more often than not — but it is a rule, and the mark says so.
Definitions, synonyms and semantic relations for sleeplessness come from Princeton University’s WordNet. Commonness is measured against a corpus of everyday English. Full sources and licences.