castle in the air
n. 空中楼阁, 白日做梦
例句与用法：
He is building castle in spain among his book.
他埋头于书本中想地天花乱坠。
词形变化：
动词过去式: castled | 动词过去分词: castled | 动词现在分词: castling | 动词第三人称单数: castles |
详细释义：
空中楼阁
What he is talking about is just a castle in the air.
他所谈论的一切, 只不过是空中楼阁。