tall order noun
[singular] informal : something that is very difficult to do
▪ Getting the project done on schedule is going to be a tall order. ▪ That's a (pretty/very) tall order. = That's a tall order to fill.
▪ Getting the project done on schedule is going to be a tall order. ▪ That's a (pretty/very) tall order. = That's a tall order to fill.
