Syllable division derived from spelling — this word is not in the pronouncing dictionary, so no phonetic transcription is shown rather than a guessed one.
regionalism is a noun meaning "a feature (as a pronunciation or expression or custom) that is characteristic of a particular region". It carries 3 recorded senses.
a feature (as a pronunciation or expression or custom) that is characteristic of a particular region
a foreign policy that defines the international interests of a country in terms of particular geographic areas
loyalty to the interests of a particular region
Forms marked · are formed by the regular rule rather than recorded in the source data. English keeps a few hundred irregulars and the rest follow the pattern, so the rule is right far more often than not — but it is a rule, and the mark says so.
Definitions, synonyms and semantic relations for regionalism come from Princeton University’s WordNet. Commonness is measured against a corpus of everyday English. Full sources and licences.