The bull graph is a simple graph on 5 nodes and 5 edges whose name derives from its resemblance to a schematic illustration of a bull or ram (whose face is the triangle and horns are the graph's two bridges). It could perhaps equally well be called the "for all-graph" or "A-graph," and unfortunately sometimes is (e.g., Farrugia 1999, p. 2), even though that term is usually applied to a particular 6-node graph.
The bull graph is implemented in the Wolfram Language as GraphData["BullGraph"].
The bull graph is also chromatically equivalent to two distinct graphs illustrated above, all of which share the chromatic polynomial 
.
