The Collaborative International Dictionary of English v.0.48:

Parallelism \Par"al*lel*ism\, n. [Gr. ?, fr. ? to place side by
   side, or parallel: cf. F. parall['e]lisme.]
   [1913 Webster]
   1. The quality or state of being parallel.
      [1913 Webster]

   2. Resemblance; correspondence; similarity.
      [1913 Webster]

            A close parallelism of thought and incident. --T.
                                                  Warton.
      [1913 Webster]

   3. Similarity of construction or meaning of clauses placed
      side by side, especially clauses expressing the same
      sentiment with slight modifications, as is common in
      Hebrew poetry; e. g.:

            At her feet he bowed, he fell:
            Where he bowed, there he fell down dead. --Judg. v.
                                                  27.
      [1913 Webster]

WordNet (r) 3.0 (2006):

parallelism
    n 1: similarity by virtue of corresponding [syn: parallelism,
         correspondence]

Moby Thesaurus II by Grady Ward, 1.0:

130 Moby Thesaurus words for "parallelism":
   accompaniment, accord, accordance, affinity, agreement, alikeness,
   allegory, alliance, analogy, aping, approach, approximation,
   assent, assimilation, balance, balancing, bilateral symmetry,
   chorus, closeness, co-occurrence, coequality, coextension,
   coherence, coincidence, community, comparability,
   comparative anatomy, comparative degree, comparative grammar,
   comparative judgment, comparative linguistics,
   comparative literature, comparative method, compare, comparing,
   comparison, compatibility, concert, concomitance, concomitancy,
   concord, concordance, concurrence, conformance, conformation,
   conformity, confrontation, confrontment, congeniality, congruence,
   congruency, congruity, consistency, consonance, consort, contrast,
   contrastiveness, cooperation, copying, correlation, correspondence,
   distinction, distinctiveness, dynamic symmetry, equality, equation,
   equilibrium, equipoise, equipollence, equiponderance, equity,
   equivalence, equivalency, eurythmics, eurythmy, evenness, finish,
   harmony, identity, imitation, intersection, justice, keeping,
   levelness, likeness, likening, matching, metaphor, mimicking,
   multilateral symmetry, nearness, oneness, opposing, opposition,
   overlap, par, parity, peace, poise, polarity, proportion,
   proportionality, rapport, regularity, relation, resemblance,
   sameness, self-consistency, semblance, shapeliness, similarity,
   simile, similitude, simulation, simultaneity, symmetricalness,
   symmetry, sync, synchronism, tally, timing, togetherness,
   trilateral symmetry, trope of comparison, uniformity, union,
   unison, unisonance, weighing, withness



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

parallelism

   1. parallel processing.

   2.  The maximum number of independent subtasks in a
   given task at a given point in its execution.  E.g. in
   computing the expression

   	(a + b) *

   (c + d) the expressions a, b, c and d can all be calculated in
   parallel giving a degree of parallelism of (at least) four.
   Once they have been evaluated then the expressions a + b and c
   + d can be calculated as two independent parallel processes.

   The Bernstein condition states that processes P and Q can be
   executed in parallel (or in either sequential order) only if:

   (i) there is no overlap between the inputs of P and the
   outputs of Q and vice versa and

   (ii) there is no overlap between the outputs of P, the outputs
   of Q and the inputs of any other task.

   If process P outputs value v which process Q reads then P must
   be executed before Q.  If both processes write to some
   variable then its final value will depend on their execution
   order so they cannot be executed in parallel if any other
   process depends on that variable's value.

   (1995-05-07)