Learn how to say Idiomatic correctly in English with this tutorial pronunciation video.
Oxford dictionary definition of the word idiomatic:
1using, containing, or denoting expressions that are natural to a native speaker:
he spoke fluent, idiomatic English
2appropriate to the style of art or music associated with a particular period, individual, or group:
a short Bach piece containing lots of idiomatic motifs
early 18th century: from Greek idiōmatikos ‘peculiar, characteristic’, from idiōma (see idiom)