What does Rub’ mean?
Since a Hizb splits into four Arba' (plural of Rub'), this smaller division helps reciters track progress in fine detail during memorization or a structured daily reading plan.
Quran Structure
Rub’
رُبْع · /rubʕ/
A Rub' is one quarter of a Hizb, one of the smaller standard units used to divide the Quran.