抹头heading back
按之窅而不起fails to spring back after pressure is released
背伤back injury
【医】 后牙, 磨牙back teeth
防静电背面层X-back【摄】
书脊上胶机book back gluing machine
让刀cutter back-off【机】;cutter relieving【机】
回溯算法back tracking algorithm【计】;back-track algorithm【计】