/ˈɑːr.bə.trer.i/
(of an action, a decision, a rule, etc. 行动、决定、规章等) not seeming to be based on a reason, system or plan and sometimes seeming unfair 任意的；武断的；随心所欲的
The choice of players for the team seemed completely arbitrary.
看来这个队的队员完全是随意选定的。
He makes unpredictable, arbitrary decisions.
他做的决定难以预料，主观武断。