OED: Adjective. Dependent on the throw of a die; hence, dependent on uncertain contingencies. (OED, 2nd Ed, accessed through U of MN Libraries)
Barzun: “Since much punctuation in printed matter today comes from the copy editor rather than the author, these shades of thought should perhaps be classed as ‘aleatory art’” (239).
Sentence: They were instructed to use an aleatory process to obtain the set of random numbers.