I don't know if it ever possible to answer the question "what is graphic design?" because it will inevitably mean something different to every graphic designer. But with this buzz I will try and describe what graphic design is to me. First to understand what graphic design is I think it is important to know what "design" is. this is the introduction/definition of what design is from wikipedia:
Design, usually considered in the context of applied arts, engineering, architecture, and other creative endeavors, is used both as a noun and a verb. As a verb, "to design" refers to the process of originating and developing a plan for a product, structure, system, or component. As a noun, "a design" is used for either the final (solution) plan (e.g. proposal, drawing, model, description) or the result of implementing that plan (e.g. object produced, result of the process). More recently, processes (in general) have also been treated as products of design, giving new meaning to the term "process design".