The Collaborative International Dictionary of English v.0.48:

Narrowing \Nar"row*ing\, n.
   1. The act of contracting, or of making or becoming less in
      breadth or extent.
      [1913 Webster]

   2. The part of a stocking which is narrowed.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Narrow \Nar"row\, v. t. [imp. & p. p. Narrowed; p. pr. & vb.
   n. Narrowing.] [AS. nearwian.]
   1. To lessen the breadth of; to contract; to draw into a
      smaller compass; to reduce the width or extent of. --Sir
      W. Temple.
      [1913 Webster]

   2. To contract the reach or sphere of; to make less liberal
      or more selfish; to limit; to confine; to restrict; as, to
      narrow one's views or knowledge; to narrow a question in
      discussion.
      [1913 Webster]

            Our knowledge is much more narrowed if we confine
            ourselves to our own solitary reasonings. --I.
                                                  Watts.
      [1913 Webster]

   3. (Knitting) To contract the size of, as a stocking, by
      taking two stitches into one.
      [1913 Webster]

WordNet (r) 3.0 (2006):

narrowing
    adj 1: becoming gradually narrower; "long tapering fingers";
           "trousers with tapered legs" [syn: tapered, tapering,
           narrowing]
    2: (of circumstances) tending to constrict freedom [syn:
       constricting, constrictive, narrowing]
    n 1: an instance of becoming narrow
    2: a decrease in width [ant: broadening, widening]
    3: the act of making something narrower [ant: broadening,
       widening]

Moby Thesaurus II by Grady Ward, 1.0:

82 Moby Thesaurus words for "narrowing":
   abbreviation, astriction, astringency, ban, bar, barring, blockade,
   bottleneck, boycott, cervix, circumscription, coarctation,
   compactedness, compaction, compression, compressure, concentration,
   condensation, confining, consolidation, constriction,
   constringency, contraction, contracture, cramping, curtailment,
   debarment, debarring, decrease, demarcation, diminuendo,
   disentanglement, disinvolvement, distillation, embargo, exception,
   exclusion, hourglass, hourglass figure, inadmissibility,
   injunction, isthmus, knitting, limitative, limiting, lockout,
   narrow place, neck, nonadmission, omission, preclusion,
   prohibition, puckering, purification, pursing, reduction,
   refinement, rejection, relegation, repudiation, restricting,
   restriction, restrictive, shortening, simplification,
   solidification, stranglement, strangulation, streamlining,
   striction, stricture, stripping, stripping down, systole, taboo,
   taper, tapering, uncluttering, unscrambling, unsnarling,
   wasp waist, wrinkling



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

narrowing

    Unification followed by unfolding.  The
   left-hand side of a rule is unified with some term, resulting in
   a set of variable bindings.  The term is then replaced by the
   right-hand side of the rule with values substituted for bound
   variables.

   (2015-01-23)