An indelible mark or substance is impossible to remove by washing or in any other way.

indelible ink 洗不掉的墨水渍

The blood had left an indelible mark on her shirt. 她衬衫上留下的血迹洗不掉。

Indelible memories or actions are impossible to forget, or have a permanent influence or effect.

I have an indelible memory of that meeting with Anastasia. 我永远忘不了那次与阿纳斯塔希亚的会面。

In his 20 years working for the company, Joe Pearson made an indelible impression on it. 在为公司工作的20年中，乔‧皮尔逊给公司留下了难以磨灭的印象。