Arbitrary means determined by chance, whim, or impulse, and not by necessity, reason, or principle. Find out the legal, mathematical, and political implications of arbitrary , and see synonyms and translations in different languages. Arbitrary definition: subject to individual will or judgment without restriction ; contingent solely upon one's discretion.. See examples of ARBITRARY used in a sentence. arbitrary - Dictionary definition and meaning for word arbitrary Definition (adj) based on or subject to individual discretion or preference or sometimes impulse or caprice Example Sentence an arbitrary decision the arbitrary rule of a dictator an arbitrary penalty of arbitrary size and shape an arbitrary choice arbitrary division of the group ... arbitrary meaning , definition , what is arbitrary : decided or arranged without any reason o...: Learn more.