(1):

(a.) Exercised according to one's own will or caprice, and therefore conveying a notion of a tendency to abuse the possession of power.

(2):

(a.) Despotic; absolute in power; bound by no law; harsh and unforbearing; tyrannical; as, an arbitrary prince or government.

(3):

(a.) Depending on will or discretion; not governed by any fixed rules; as, an arbitrary decision; an arbitrary punishment.