Source : Webster's Revised Unabridged Dictionary (1913)

Aleatory \A"le*a*to*ry\, a. [L. aleatorius, fr. alea chance,
   die.] (Law)
   Depending on some uncertain contingency; as, an aleatory
   contract. --Bouvier.

Source : WordNet®

aleatory
     adj : dependent on chance; "the aleatory element in life"