Business definition excludes activities by government or local authorities as public authorities, clarifying GST applicability. An explanation is inserted to clarify that, for the purposes of the relevant item in notification No. 46/ST-2, the term 'business' does not include any activity or transaction undertaken by the Central Government, a State Government or any local authority in which they are engaged as public authorities, thereby excluding such government or local authority activities from the scope of 'business' for GST applicability under the notification.