The boy gave the bully a pelt on the back with a pebble.那男孩用石子掷击小流氓的背脊。His back was twitching with pain.他的背脊因疼痛而抽搐着。He was bothered with an itching back.他背脊发痒很不好受。A chill ran up/down my spine.我的背脊感到一阵寒战。He felt the rain driving at his back.他感到雨在抽打着他的背脊。