unmarked expression的用法和樣例：
例句
- Reports say the hikers ignored warnings and straightly crossed the unmarked border between northern Iraq and Iran.
報告稱這些旅客不顧警告直接穿越伊拉克北部和伊朗無標記的邊境。 - The driver of any vehicle shall yield the right of way to a pedestrian on any portion of any unpaved road or crossing within any marked or unmarked crosswalk of a paved road.
任何交通工具的駕駛員將把右側讓給在沒有鋪石磚的道路任何一部分，或在鋪設道路有標記的或無標記的人行橫道以內的行人。
