The Collaborative International Dictionary of English v.0.48:

Stochastic \Sto*chas"tic\ (st[-o]*k[a^]s"t[i^]k), a. [Gr.
   stochastiko`s, from stocha`zesqai to aim, to guess, fr.
   sto`chos mark or aim.]
   1. Conjectural; able to conjecture. [Obs.] --Whitefoot.
      [1913 Webster]

   2. random; chance; involving probability; opposite of
      deterministic.
      [GG]

   3. (Statistics) of or pertaining to a process in which a
      series of calculations, selections, or observations are
      made, each one being randomly determined as a sample from
      a probability distribution.

   Note: Where physical phenomena are modelled as a stochastic
         process, each subsequent calculation of a series may
         depend on the result of the previous calculation, as in
         the modelling of the process of diffusion of molecules.
         Many series may be calculated, and the results
         averaged, to estimate the most likely result. See also
         Markov chain.
         [PJC] -- sto*chas"tic*al*ly, adv.
         [PJC]

WordNet (r) 3.0 (2006):

stochastic
    adj 1: being or having a random variable; "a stochastic
           variable"; "stochastic processes"

Moby Thesaurus II by Grady Ward, 1.0:

63 Moby Thesaurus words for "stochastic":
   aimless, aleatoric, aleatory, amorphous, blobby, blurred, blurry,
   broad, casual, causeless, chance, chancy, chaotic, confused,
   designless, disordered, driftless, dysteleological, foggy, fuzzy,
   general, haphazard, hazy, hit-or-miss, ill-defined, imprecise,
   inaccurate, inchoate, incoherent, indecisive, indefinable,
   indefinite, indeterminable, indeterminate, indiscriminate,
   indistinct, inexact, inexplicable, lax, loose, mindless,
   nonspecific, obscure, orderless, promiscuous, purposeless, random,
   shadowed forth, shadowy, shapeless, stray, sweeping, unaccountable,
   unclear, undefined, undestined, undetermined, undirected,
   unmotivated, unplain, unspecified, vague, veiled



The Free On-line Dictionary of Computing (30 December 2018):

probabilistic
stochastic

    Relating to, or governed by, probability. The
   behaviour of a probabilistic system cannot be predicted
   exactly but the probability of certain behaviours is known.
   Such systems may be simulated using pseudorandom numbers.
   Evolutionary computation uses probabilistic processes to
   generate new (potential) solutions to a problem.

   See also deterministic, non-probabilistic.

   (1995-09-22)