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]

The Free On-line Dictionary of Computing (19 January 2023):

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)