Syllable division derived from spelling — this word is not in the pronouncing dictionary, so no phonetic transcription is shown rather than a guessed one.
thriftlessness is a noun meaning "the trait of wasting resources". It carries one recorded sense.
the trait of wasting resources
“a life characterized by thriftlessness and waste”
“the wastefulness of missed opportunities”
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 thriftlessness come from Princeton University’s WordNet. Commonness is measured against a corpus of everyday English. Full sources and licences.