unidiomatic
/ˌʌnɪdiəˈmætɪk/
adjective
- Not following the natural or usual way that native speakers of a language express something; not idiomatic.
- Using 'big rain' instead of 'heavy rain' is unidiomatic in English.
- The phrase 'make a decision on' is not wrong, but 'decide on' sounds unidiomatic in this context.
- Her translation was grammatically correct but felt unidiomatic to a native English speaker.