Syllable division derived from spelling — this word is not in the pronouncing dictionary, so no phonetic transcription is shown rather than a guessed one.
rumbustious is an adjective meaning "noisy and lacking in restraint or discipline". It carries one recorded sense.
noisy and lacking in restraint or discipline
“a boisterous crowd”
“a social gathering that became rambunctious and out of hand”
“a robustious group of teenagers”
“beneath the rumbustious surface of his paintings is sympathy for the vulnerability of ordinary human beings”
“an unruly class”
Definitions, synonyms and semantic relations for rumbustious come from Princeton University’s WordNet. Commonness is measured against a corpus of everyday English. Full sources and licences.