مُبْهَمٌ: وَهُوَ مَا لَا يَكُونُ لَهُ حَدٌّ مُعَيَّنٌ، كَـ«دَهْرٍ» وَ«حِينٍ».
Translation: An unspecified time expression has no fixed boundary in its lexical meaning, such as dahr (a period) and ḥīn (a while).
Dahr and ḥīn do not themselves specify a fixed measure. Context may clarify duration, without changing their lexical classification.