Syllable division derived from spelling — this word is not in the pronouncing dictionary, so no phonetic transcription is shown rather than a guessed one.
z-axis is a noun meaning "the third axis in a 3-dimensional coordinate system". It carries one recorded sense.
the third axis in a 3-dimensional coordinate system
Definitions, synonyms and semantic relations for z-axis come from Princeton University’s WordNet. Commonness is measured against a corpus of everyday English. Full sources and licences.