Various terms are used to denote the field/area/academic stream we belong to in our scholarly ventures: teaching, research and/or other activities. But discipline is a much wider and more generalized term used in academics. Professors sometime claim their discipline to be their academic home; and sometime inter-, cross- or multi-disciplinary studies are much in advocacy. But is that all? Does a discipline have some boundaries or barricades? Or 'a discipline' is just an act of disciplining different subjects/academics?
NB: I find dictionary meanings misleading. For quotations, pl. provide references.