Maru has many meanings in Japanese:
(1) Round.
(2) Circle. ○-shaped symbol indicating correctness, excellence, etc.
(3) (common saying) money.
(4) Area. A division within the city
(5) Circle. Punctuation marks include periods and semi-voiced sounds.
(6) Completely, completely. As is. Full, whole.
(7) (joint) whole, full.
(8) (Connectors) All, all inclusive. It means that it is completely in a certain state