If you say that someone is being unrealistic, you mean that they do not recognize the truth about a situation, especially about the difficulties involved in something they want to achieve.
双语例句
例： There are many who feel that the players are being completely unrealistic in their demands.
许多人都觉得那些运动员的要求是完全不切实际的。
例： It would be unrealistic to expect such a process ever to be completed.
想要完成这样一个过程是不现实的。