mirage

1. N-COUNT A mirage is something that you see when it is extremely hot, for example in the desert, and which appears to be quite near but is actually a long way away or does not really exist. 海市蜃楼; 幻境

It hovered before his eyes like the mirage of an oasis. 它在他眼前晃动，好像海市蜃楼里的绿洲。

2. N-COUNT If you describe something as a mirage, you mean that it is not real or true, although it may seem to be. 幻想; 妄想[usu sing]

The girl was a mirage, cast up by his troubled mind. 那个女孩是他的幻觉，是他混乱的头脑中妄想出来的。