Plain, simple, or subdued in appearance; not flashy (used for colors, designs, clothing, etc.).
彼女はいつも地味な服を選ぶ。
She always chooses plain/classic clothes.
地味な色のコートが冬には重宝する。
A subdued-colored coat is useful in winter.
派手なデザインより地味なほうが好みだ。
I prefer plain over flashy designs.
Reserved or modest behavior; unobtrusive and quiet manner or personality.
彼は地味な性格で、目立ちたがらない。
He has a modest personality and doesn't like to stand out.
彼女は派手ではなく地味に振る舞うタイプだ。
She's the type to act modestly rather than flamboyantly.
Colloquial adverb 'jimi ni' meaning 'a bit/quite' in the sense of subtly, modestly, or surprisingly (can be positive or negative).
このアプリは地味に便利だ。
This app is quietly useful.
その映画は地味に面白くて最後まで見てしまった。
That movie was surprisingly interesting in a subtle way, and I watched it to the end.
彼の発言は地味に場を和ませた。
His remark subtly lightened the mood.