1. 难忘的;不可磨灭的
If you say that something leaves an indelible impression, you mean that it is very unlikely to be forgotten.
e.g. My visit to India in 1986 left an indelible impression on me...
1986年的印度之行给我留下了难忘的印象。
e.g. The war has made an indelible mark on the world.
战争给世人留下了不可磨灭的印记。
indeliblyThe horrors he experienced are imprinted, perhaps indelibly, in his brain.
他经历的恐怖事件在他脑海中刻下了深深的,或许是难以磨灭的印记。
2. 难以去除的;洗不掉的;擦不掉的
Indelible ink or an indelible stain cannot be removed or washed out.
e.g. It leaves indelible stains on clothes.
它会在衣物上留下洗不掉的污渍。
e.g. ...written in indelible ink.
用不褪色墨水写就