The Collaborative International Dictionary of English v.0.48:

Graph \Graph\ (gr[.a]f), n. [See -graph.] (Math.)
   1. A curve or surface, the locus of a point whose coordinates
      are the variables in the equation of the locus; as, a
      graph of the exponential function.
      [Webster 1913 Suppl.]

   2. A diagram symbolizing a system of interrelations of
      variable quantities using points represented by spots, or
      by lines to represent the relations of continuous
      variables. More than one set of interrelations may be
      presented on one graph, in which case the spots or lines
      are typically distinguishable from each other, as by
      color, shape, thickness, continuity, etc. A diagram in
      which relationships between variables are represented by
      other visual means is sometimes called a graph, as in a
      bar graph, but may also be called a chart.
      [Webster 1913 Suppl. +PJC]

WordNet (r) 3.0 (2006):

bar graph
    n 1: a chart with bars whose lengths are proportional to
         quantities [syn: bar chart, bar graph]