备用二级头呼吸器 bèiyòng'èrjítóuhūxīqì octopus Origin Definitions Defs Strokes Stroke Words Sentences Sents 备用 備用 bèiyòng adjective reserve; spare; backup to keep in reserve for future use; ready for use as a backup or standby二级头呼吸器 二級頭呼吸器 èrjítóuhūxīqì regulator; demand valve (scuba diving) second-stage regulator; a device that reduces air pressure to a breathable level upon inhalation