backpa[机] 背板backn.后面；背脊；靠背；后背；后卫vt.支持；后退adv.向后地adj.向后的；后面的；偏远的；过时的；积欠的back lining腔背,背衬,安全衬砖层back access背径小路back sloper刮沟刀back-bulb衰老球根backscattern.反向散射；背反射=backscattering.back center尾顶尖back letter认赔书back pay.欠薪back filter反回过滤Backmeister巴克迈斯特