Backal口腔锭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backing strap衬垫Back-ejecta回喷back-sihing回淤back twisting反向加捻back grouting桩底注浆backdiffusionn.反行扩散；反向扩散 背面扩散back-comingn.后退式回采backwash rate反冲速度back recovery返回恢复back rigidity脊强