1Plain, subdued, or sober in color or appearance; not flashy.
面接には地味な色のスーツを選んだ。
I chose a suit in a subdued color for the interview.
このバッグはデザインが地味で、どんな服にも合わせやすい。
This bag has a plain design, so it's easy to match with any outfit.
派手なネクタイより地味なほうが仕事には向いている。
A subdued tie is more suitable for work than a flashy one.
母は年齢のせいか、最近服の趣味が地味になってきた。
Maybe because of her age, my mother's taste in clothes has become more subdued lately.
2Reserved, modest, or unobtrusive in behavior or attitude.
彼は地味な性格で、パーティーでもあまり話さない。
He has a reserved personality and doesn't talk much even at parties.
新入社員は地味だが、仕事は誰よりも丁寧だ。
The new employee is unassuming, but does more careful work than anyone else.
3(Colloquial, as 地味に) meaning "surprisingly" or "in a low-key way" — used positively or negatively.
この参考書は地味に役に立つ。
This reference book is surprisingly useful.
毎日の腹筋は地味にきつい。
Doing sit-ups every day is more grueling than it looks.
彼の一言が地味に傷ついた。
His remark quietly hurt me more than I expected.