Electrically, a node is any
continuous section of a
circuit sharing the same
voltage. Typically this occurs at the
junction of different
components, but a node is
not just the junction.
See also node analysis.
As an extra thought: Since any number of components can be connected to a node, it can used as a method for locating components. If one names each node, and then indicates, for each component, which terminals of the component connect to which nodes, one has an unambiguous mapping of a circuit; this is, for example, the approach that spice uses.