ultimate = 至极的，最终的update = 更新，更新换代unable = 无能为力unauthorized = 未经授权unclear = 不明确underbrush = 灌木丛undergo = 遭受undersecretary = 副秘书长undoubted = 毫无疑问的uneasy = 不安的unsafe = 不安全的up to = 至upcoming = 即将到来的upgrade = 升级usher = 引座员
