2N-UNCOUNT 妄想;幻想Delusion is the state of believing things that are not true. 妄想;幻想
This was not optimism, it was delusion.
这不是乐观,这是妄想。
3PHRASE 妄自尊大;自以为是 If someone has delusions of grandeur, they think and behave as if they are much more important or powerful than they really are. 妄自尊大;自以为是 [disapproval]
He suggested that we suffer delusions of grandeur as a football nation.
他暗示我们妄自尊大地以为自己是个足球民族。
...mansions built by men with delusions of grandeur.