Aleatory

adj. contingent upon a future event, depending on luck, occasional

Aleatory means "pertaining to luck", and derives from the Latin word alea, the rolling of dice. Aleatoric, indeterminate, or chance art is that which exploits the principle of randomness.
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Adjective
1. dependent on chance; "the aleatory element in life"
(similar) unpredictable

(a.)
Depending on some uncertain contingency; as, an aleatory contract.
  

Synonyms and related words:
Nachtmusik, absolute music, accidental, adaptation, adventitious, adventurous, air varie, aleatoric, aleatory music, amorphous, arrangement, blobby, blurred, blurry, broad, casual, causeless, chamber music, chamber orchestra, chance, chancy, chaotic, circumstantial, composition, conditional, confused, contingent, descant, destinal, dicey, disordered, electronic music, etude, exercise, fatal, fatidic, fluky, foggy, fortuitous, full of risk, fuzzy, general, harmonization, hazardous, hazy, hit-or-miss, iffy, ill-defined, imprecise, inaccurate, inchoate, incidental, incidental music, incoherent, indecisive, indefinable, indefinite, indeterminable, indeterminate, indistinct, inessential, inexact, instrumental music, invention, lax, loose, nocturne, nonessential, nonspecific, obscure, occasional, opus, orchestration, orderless, piece, production, program music, provisional, random, ricercar, riskful, risky, score, shadowed forth, shadowy, shapeless, sonata, sonatina, speculative, stochastic, string orchestra, string quartet, study, sweeping, theme and variations, trio, uncaused, unclear, undefined, undestined, undetermined, unessential, unexpected, unforeseeable, unforeseen, unlooked-for, unplain, unpredictable, unspecified, vague, variation, veiled, venturesome, venturous, wildcat, work,