Syllable division derived from spelling — this word is not in the pronouncing dictionary, so no phonetic transcription is shown rather than a guessed one.
motiveless is an adjective meaning "occurring without motivation or provocation". It carries one recorded sense.
occurring without motivation or provocation
“motiveless malignity”
“unprovoked and dastardly attack”
Definitions, synonyms and semantic relations for motiveless come from Princeton University’s WordNet. Commonness is measured against a corpus of everyday English. Full sources and licences.