基本解释[动力][车辆] 下止点英英字典柯林斯英英字典 the position of the crank of a reciprocating engine when the piston is at its nearest point to the crankshaft (Also called outer dead centre) bottom dead centre剑桥字典bottom dead centre柯林斯字典专业释义交通运输工程下止点下死点物理学下止点下死点