Line of nodes

Node \Node\ (n[=o]d), n. [L. nodus; perh. akin to E. knot. Cf.
   {Noose}, {Nowed}.]
   1. A knot, a knob; a protuberance; a swelling.
      [1913 Webster]

   2. Specifically:
      (a) (Astron.) One of the two points where the orbit of a
          planet, or comet, intersects the ecliptic, or the
          orbit of a satellite intersects the plane of the orbit
          of its primary.
      (b) (Bot.) The joint of a stem, or the part where a leaf
          or several leaves are inserted.
      (c) (Dialing) A hole in the gnomon of a dial, through
          which passes the ray of light which marks the hour of
          the day, the parallels of the sun's declination, his
          place in the ecliptic, etc.
      (d) (Geom.) The point at which a curve crosses itself,
          being a double point of the curve. See {Crunode}, and
          {Acnode}.
      (e) (Mech.) The point at which the lines of a funicular
          machine meet from different angular directions; --
          called also {knot}. --W. R. Johnson.
      (f) (Poet.) The knot, intrigue, or plot of a piece.
      (g) (Med.) A hard concretion or incrustation which forms
          upon bones attacked with rheumatism, gout, or
          syphilis; sometimes also, a swelling in the
          neighborhood of a joint. --Dunglison.
      (h) (Mus) One of the fixed points of a sonorous string,
          when it vibrates by aliquot parts, and produces the
          harmonic tones; nodal line or point.
      (i) (Zool.) A swelling.
          [1913 Webster]

   3. (Math., Computers) A special point in a graph or diagram
      which is attached to other points by {links}. It is often
      labeled and represented graphically as a box or circle. A
      node may represent any object which is related to other
      objects in a conceptual structure that can be represented
      as a graph, the relations being represented as links
      between the nodes.
      [PJC]

   4. (Anat.) A small mass of tissue differing from other tissue
      in its immediate vicinity; as, a lymph node.
      [PJC]

   {Ascending node} (Astron.), the node at which the body is
      passing northerly, marked with the symbol [astascending],
      called the Dragon's head. Called also {northern node}.

   {Descending node}, the node at which the body is moving
      southwardly, marked thus [astdescending], called Dragon's
      tail.

   {Line of nodes}, a straight line joining the two nodes of an
      orbit.
      [1913 Webster]