The Collaborative International Dictionary of English v.0.48:

Inverse \In*verse"\, a. [L. inversus, p. p. of invertere: cf. F.
   inverse. See Invert.]
   [1913 Webster]
   1. Opposite in order, relation, or effect; reversed;
      inverted; reciprocal; -- opposed to direct.
      [1913 Webster]

   2. (Bot.) Inverted; having a position or mode of attachment
      the reverse of that which is usual.
      [1913 Webster]

   3. (Math.) Opposite in nature and effect; -- said with
      reference to any two operations, which, when both are
      performed in succession upon any quantity, reproduce that
      quantity; as, multiplication is the inverse operation to
      division. The symbol of an inverse operation is the symbol
      of the direct operation with -1 as an index. Thus sin-1 x
      means the arc or angle whose sine is x.
      [1913 Webster]

   Inverse figures (Geom.), two figures, such that each point
      of either figure is inverse to a corresponding point in
      the order figure.

   Inverse points (Geom.), two points lying on a line drawn
      from the center of a fixed circle or sphere, and so
      related that the product of their distances from the
      center of the circle or sphere is equal to the square of
      the radius.

   Inverse ratio, or Reciprocal ratio (Math.), the ratio of
      the reciprocals of two quantities.

   Inverse proportion, or Reciprocal proportion, an equality
      between a direct ratio and a reciprocal ratio; thus, 4 : 2
      : : 1/3 : 1/6, or 4 : 2 : : 3 : 6, inversely.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Inverse \In"verse\, n.
   That which is inverse.
   [1913 Webster]

         Thus the course of human study is the inverse of the
         course of things in nature.              --Tatham.
   [1913 Webster]

WordNet (r) 3.0 (2006):

inverse
    adj 1: reversed (turned backward) in order or nature or effect
           [syn: inverse, reverse]
    2: opposite in nature or effect or relation to another quantity
       ; "a term is in inverse proportion to another term if it
       increases (or decreases) as the other decreases (or
       increases)" [ant: direct]
    n 1: something inverted in sequence or character or effect;
         "when the direct approach failed he tried the inverse"
         [syn: inverse, opposite]

Moby Thesaurus II by Grady Ward, 1.0:

79 Moby Thesaurus words for "inverse":
   adversative, adverse, adversive, antagonistic, anti, antipathetic,
   antipodal, antipode, antipodes, antipole, antithesis, antithetic,
   antonym, antonymous, at cross-purposes, balancing, change,
   clashing, compensating, conflicting, confronting, contra,
   contradictory, contradistinct, contrapositive, contrarious,
   contrary, contrasted, converse, counter, counterbalance,
   counterbalancing, countercheck, counterpoint, counterpoise,
   counterpoised, counterpole, counterterm, countervailing,
   dead against, discordant, discrepant, eyeball to eyeball,
   eyeball-to-eyeball, facing, foil, heads, hostile, inconsistent,
   inimical, invert, obverse, offset, opposed, opposing, opposite,
   opposite number, opposite side, oppositional, oppositive,
   oppugnant, other face, other side, perverse, polar, polaric,
   polarized, repugnant, reverse, revert, setoff, squared off, tails,
   the contrary, the other side, transplace, transpose, turn,
   vis-a-vis



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

inverse

    Given a function, f : D -> C, a function g : C
   -> D is called a left inverse for f if for all d in D, g (f d)
   = d and a right inverse if, for all c in C, f (g c) = c and an
   inverse if both conditions hold.  Only an injection has a
   left inverse, only a surjection has a right inverse and only
   a bijection has inverses.  The inverse of f is often written
   as f with a -1 superscript.

   (1996-03-12)