tall order
US /tɔl ˈɔr.dər/
UK /tɔl ˈɔr.dər/

1.
艱鉅的任務, 苛刻的要求
a request or task that is difficult to fulfill or achieve
:
•
Finishing this project by tomorrow is a tall order.
明天之前完成這個項目是個艱鉅的任務。
•
Asking him to change his mind now is a tall order.
現在讓他改變主意是個艱鉅的任務。