Syllable division derived from spelling — this word is not in the pronouncing dictionary, so no phonetic transcription is shown rather than a guessed one.
curtainless is an adjective meaning "not provided with curtains". It carries one recorded sense.
not provided with curtains
“blank, curtainless windows stared back at her”
Definitions, synonyms and semantic relations for curtainless come from Princeton University’s WordNet. Commonness is measured against a corpus of everyday English. Full sources and licences.