Source : Webster's Revised Unabridged Dictionary (1913)

Orthogonal \Or*thog"o*nal\, a. [Cf. F. orthogonal.]
   Right-angled; rectangular; as, an orthogonal intersection of
   one curve with another.

   {Orthogonal projection}. See under {Orthographic}.

Source : WordNet®

orthogonal
     adj 1: not pertinent to the matter under consideration; "an issue
            extraneous to the debate"; "the price was immaterial";
            "mentioned several impertinent facts before finally
            coming to the point" [syn: {extraneous}, {immaterial},
             {impertinent}]
     2: statistically unrelated
     3: having a set of mutually perpendicular axes; meeting at
        right angles; "wind and sea may displace the ship's center
        of gravity along three orthogonal axes"; "a rectangular
        Cartesian coordinate system" [syn: {rectangular}]

Source : Free On-Line Dictionary of Computing

orthogonal
     
         At 90 degrees (right angles).
     
        N mutually orthogonal {vectors} {span} an N-dimensional
        {vector space}, meaning that, any vector in the space can be
        expressed as a {linear combination} of the vectors.  This is
        true of any set of N {linearly independent} vectors.
     
        The term is used loosely to mean mutually independent or well
        separated.  It is used to describe sets of primitives or
        capabilities that, like linearly independent vectors in
        geometry, span the entire "capability space" and are in some
        sense non-overlapping or mutually independent.  For example,
        in logic, the set of operators "not" and "or" is described as
        orthogonal, but the set "nand", "or", and "not" is not
        (because any one of these can be expressed in terms of the
        others).
     
        Also used loosely to mean "irrelevant to", e.g. "This may be
        orthogonal to the discussion, but ...", similar to "going off
        at a tangent".
     
        See also {orthogonal instruction set}.
     
        [{Jargon File}]
     
        (2002-12-02)