Synonyms for Idiomatic:

adj.

colloquial (adjective)
slang, conversational, colloquial, vernacular, informal, casual.
informal (adjective)
dialectal, vernacular, colloquial, local, natural.
pert (adjective)
idiomatical.
regional (adjective)
dialectal.

n.

figurative, creole, extinct, cognate, classical, figuratively, disyllabic, dead, agglutinative. discursive, clean, diffuse, circuitous, chatty, economical, declamatory, crisp, articulate. idiomatic (noun)
idiomatical.
informal (noun)
local, dialectal, natural.

Other synonyms:

disyllabic, agglutinative, figuratively, cognate. extinct, creole, figurative. classical. dead.

Usage examples for idiomatic

  1. Franklin, frozen and repelled by what he thought the bigotry of Boston, sought very early in his life the more congenial atmosphere of Philadelphia, where he found a public for his copious writings, which, if not precisely literature, were, at any rate, examples of strong, idiomatic English, conveying the shrewd philosophy of an original mind. – William Hickling Prescott by Harry Thurston Peck