top n.顶部；顶；上面；极点；陀螺adj.最高的；顶端的vt.形成顶部；达到…的顶端；处于…的最前头vi.总结；超越；高耸；结束
双语例句
You need to clean off your plate before dessert. 上甜点前你必须吃光你盘子里的东西。
The spark is therefore timed to occur before the piston reaches top dead center, otherwise maximum pressure would not be reached in time. 因而，在活塞到达上死点前，火花便会发生，否则就不可能适时达到最高的压力。
