The Collaborative International Dictionary of English v.0.48:

matrix \ma"trix\ (m[=a]"tr[i^]ks), n.; pl. Matrices
   (m[a^]t"r[i^]*s[=e]z). [L., fr. mater mother. See Mother,
   and cf. Matrice.]
   [1913 Webster]
   1. (Anat.) The womb.
      [1913 Webster]

            All that openeth the matrix is mine.  --Ex. xxxiv.
                                                  19.
      [1913 Webster]

   2. Hence: That which gives form or origin to anything; as:
      (a) (Mech.) The cavity in which anything is formed, and
          which gives it shape; a die; a mold, as for the face
          of a type.
      (b) (Min.) The earthy or stony substance in which metallic
          ores or crystallized minerals are found; the gangue.
      (c) pl. (Dyeing) The five simple colors, black, white,
          blue, red, and yellow, of which all the rest are
          composed.
          [1913 Webster]

   3. (Biol.) The lifeless portion of tissue, either animal or
      vegetable, situated between the cells; the intercellular
      substance.
      [1913 Webster]

   4. (Math.) A rectangular arrangement of symbols in rows and
      columns. The symbols may express quantities or operations.
      [1913 Webster]

WordNet (r) 3.0 (2006):

matrix
    n 1: (mathematics) a rectangular array of quantities or
         expressions set out by rows and columns; treated as a
         single element and manipulated according to rules
    2: (geology) amass of fine-grained rock in which fossils,
       crystals, or gems are embedded
    3: an enclosure within which something originates or develops
       (from the Latin for womb)
    4: the body substance in which tissue cells are embedded [syn:
       matrix, intercellular substance, ground substance]
    5: the formative tissue at the base of a nail
    6: mold used in the production of phonograph records, type, or
       other relief surface

Moby Thesaurus II by Grady Ward, 1.0:

63 Moby Thesaurus words for "matrix":
   Platonic form, Platonic idea, aesthetic form, archetype, art form,
   build, cast, chimney, chute, configuration, conformation,
   country rock, cut, deposit, die, dike, fashion, figuration, figure,
   form, format, formation, frame, gangue, genre, impression,
   inner form, intaglio, last, layout, lode, lodestuff, make, makeup,
   mineral deposit, mint, modality, mode, model, mold, negative,
   ore bed, pattern, pay dirt, prototype, punch, seal, set, shape,
   shoe last, shoot, significant form, stamp, stock, structure, style,
   template, turn, type, uterus, vein, venter, womb



The Jargon File (version 4.4.7, 29 Dec 2003):

Matrix
 n.

    [FidoNet]

    1. What the Opus BBS software and sysops call FidoNet.

    2. Fanciful term for a cyberspace expected to emerge from current
    networking experiments (see the network). The name of the rather good
    1999 cypherpunk movie The Matrix played on this sense, which however had
    been established for years before.

    3. The totality of present-day computer networks (popularized in this sense
    by John Quarterman; rare outside academic literature).


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

Matrix

   [FidoNet]  1. What the Opus BBS software and sysops call
   FidoNet.

   2. Fanciful term for a cyberspace expected to emerge from
   current networking experiments (see network, the).

   3. The totality of present-day computer networks.

   [Jargon File]