Syllable division derived from spelling — this word is not in the pronouncing dictionary, so no phonetic transcription is shown rather than a guessed one.
one-trillionth is a noun meaning "one part in a trillion equal parts". It carries one recorded sense.
one part in a trillion equal parts
Definitions, synonyms and semantic relations for one-trillionth come from Princeton University’s WordNet. Commonness is measured against a corpus of everyday English. Full sources and licences.