indelible

1. ADJ If you say that something leaves an indelible impression, you mean that it is very unlikely to be forgotten. 难忘的[usu ADJ n]

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。

2. indeliblyADV [ADV with v]

The 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，也许是难以磨灭的印记。

3. ADJ Indelible ink or an indelible stain cannot be removed or washed out. (污渍)洗不掉的[usu ADJ n]

It leaves indelible stains on clothes. 它会在衣物上留下洗不掉的污渍。

The message was written in indelible ink. 这条信息是用不褪色的墨水写的。