采购订单中，应该是Authorized economic operator的缩写，译为“经认证的经营者”。具体的含义可以参考海关总署网站，如下：

AEO是Authorized Economic Operator的简称，即“经认证的经营者”，是世界海关组织倡导的，通过海关对信用状况、守法程度和水平较高的企业进行认证，对通过认证的企业给予优惠通关便利的一项制度。互认安排实施后，两国AEO企业将享受到双方给予的降低单证审核和货物查验率、加快通关速度、实施优先查验、通过设立联络员沟通解决企业通关中遇到的问题等多项便利措施。双方企业货物通关时间有望明显压缩，港口、保险、物流等贸易成本也将相应得以降低。

相关的英文释义可参考Wikipedia：

According to the World Customs Organization (WCO), an authorized economic operator (AEO) is

"a party involved in the international movement of goods in whatever function that has been approved by or on behalf of a national Customs administration as complying with WCO or equivalent supply chain security standards. Authorized Economic Operators include inter alia manufacturers, importers, exporters, brokers, carriers, consolidators, intermediaries, ports, airports, terminal operators, integrated operators, warehouses and distributors"

参考

Wikipedia

www.gov.cn