[] the most important part of a system, an organization, etc.支柱；基础◆Small and medium-sized businesses are the backbone of the economy.中小企业是经济的支柱。 () the system of connections that carries information long distances over the Internet主干网，骨干网（通过互联网长距离传输信息的连接系统）◆ The high-speed Internet backbone has to deal with more and more traffic every day.高速骨干网每天必须处理越来越多的传输信息。