前后比forward: adv. 1.向前,前进 (opp. backward) ...back: n. 1.背,背部;背脊;背面,反面;背后,后部,后面, ...ratio: n. (pl. ratios) 1.比,比率,比值;比例 ...forward and back: 前进与后退back circle forward: 后撑前回环下载手机词典可随时随地查词查翻译