/ ˈɑːbɪtrəri; ˈɑːbɪtri; NAmE ˈɑːrbətreri/ adjective
1.
( of an action, a decision, a rule, etc. ) not seeming to be based on a reason, system or plan and sometimes seeming unfair :
The choice of players for the team seemed completely arbitrary.
He makes unpredictable, arbitrary decisions.
2.
( formal ) using power without restriction and without considering other people :
the arbitrary powers of officials
► ar·bi·trar·ily / ˌɑːbɪˈtrerəli; ˈɑːbɪtrəli; NAmE ˌɑːrbəˈt-/ adverb :
The leaders of the groups were chosen arbitrarily.
► ar·bi·trari·ness noun [ U ]
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WORD ORIGIN
late Middle English (in the sense dependent on one's will or pleasure, discretionary ): from Latin arbitrarius , from arbiter judge, supreme ruler, perhaps influenced by French arbitraire .