翻译：“不地道的表达”

It's not a local answer !
It's not a local color answer .

broken expression??

it's awkward

The expression is not idiomatic.

idiomatic a.1. 惯用语句的,2. 符合语言习惯的,具有语言特点的

He speaks idiomatic English.
他说道地的英语。

unconventional expression

non-local expression