backwardi滞后backwardadj.向后的；落后的adv.向后backward extruding反挤压Backward Advantage后发优势backward algorithm逆序算法backward wave tube回波管backward selection逆向选择backward provinces落后省区backward-surgingadj.逆涌；后涌backward induction逆向归纳法backward direction反向, 后向backward signaling反向信令