Syllable division derived from spelling — this word is not in the pronouncing dictionary, so no phonetic transcription is shown rather than a guessed one.
master-at-arms is a noun meaning "the senior petty officer; responsible for discipline aboard ship". It carries one recorded sense.
the senior petty officer; responsible for discipline aboard ship
Definitions, synonyms and semantic relations for master-at-arms come from Princeton University’s WordNet. Commonness is measured against a corpus of everyday English. Full sources and licences.