U字头 A: What would you ultimate vacation be? B: I’d love to go to Europe ultimate a. 1.极端的，最大的，最高的；2。最后的，最终的 n. 终极，顶点，极限 A: It is really raining outside. Do you have an umbrella I could borrow? B: Yes, feel free to take with you . I have another one that I can use. umbrella n. 雨伞 A: They didn’t uncover any evidence that would prove her guilty of the crime. B: I’m not surprised, because I’m certain she is innocent. uncover vt. 1。揭露，暴露；2。揭开……的盖子 A: He will have to undergo surgery to correct the problem with his knee. B: Isn’t there an alternative? undergo vt. 经历，遭受 A: What sort of training have you had as a teacher? B: I did my undergraduate work in Child Psychology, and received my Mater’s degree in Education. undergraduate n. 大学本科生 A: Where are the telephone lines located in this neighborhood? B: My understanding is that they are all underground. underground a. 1。地（面）下的；2。秘密地，不公开地 ad. 1。在地（面）下，往地（面）下；2。秘密地，不公开地 n. 1。地铁；2。地下组织（或运动） A: Please underline all of the book titles in your paper. B: Do I capitalize every word in the title of the books? underline vt. 1。在……下面划线；2。强调，使突出 A: I’ve lost my shoes. B: Have you looked underneath the chair? underneath prep. 在……下面，在……底下 ad. 在下面，在底下 n. 下部，地部 A: Do you know when these reports are due? B: My understanding is that we need to have them in by Friday. understanding n. 1。谅解，（非正式）协议；2。理解（力）；3。相互理解，融洽 a. 体谅的，宽容的，通情达理的 A: That’s a mighty big project to undertake in such a shout amount of time. B: I know, but I really believe I can get it done. undertake vt. 1。承担，着手做；2。同意，答应，保证 A: It’s really hard to undo a mistake like that one. B: Maybe we could just start over. undo vt. 1。解开，松开；2。取消，撤消 A: Undoubtedly , there is still work to be done on this driveway. B: I agree. After a rain, the ruts form all over again. undoubtedly ad. 无疑，必定 A: Why don’t you meet us for dinner in about an hour? B: I’m sorry, but we have some unexpected visitors in town tonight. unexpected a. 想不到的，意外的 A: Unfortunately , I left my keys at home. B: Don’t worry, I have an extra set. unfortunately ad. 遗憾的是，可惜的是 A: It’s hard to imagine anyone not being touched by the union of black and red in this painting. B: The artist really did do an amazing job. union n. 1。工会，联盟；2。结合，联合，合并 A: You have unique way of expressing yourself that is very engaging. B: Thank you. I really appreciate the complement. unique a. 1。唯一的，独特的，独一无二的；2。极不寻常的，极好的 A: There seems to be a unity on their team that is very effective. B: I agree. They really know how to work together toward a common goal. unity n. 1。团结，联合，统一；2。和睦，协调 A: The universal need for love ties all of humanity together. B: What about the universal need for food? universal a. 1。普遍的，全体的；2。通用的，万能的；3。宇宙的，全世界的 A: The universe is so large that it takes years to travel from one planet to another. B: Perhaps with the new technologies things will happen faster. universe n. 1。宇宙，万物，世界；2。领域，范围 A: Unlike yesterday, the air seems very cold today. B: I’m sure the wind chill factor is part of the reason. unlike prep. 不像，和……不同 A: If I unload the bricks from my car, I’ll have room for one more passenger. B: Here, I’ll help you. unload vt. 1。卸（货），从……卸下货物；下（客）；2。退出（枪的）子弹，卸下（相机的）胶卷 vi. 卸货；下客 A: It’s quite unusual to see deer crossing the highway. B: They must be fleeing from hunters. unusual a. 1。不平常的，少有的；2。与众不同的，独特的 A: The upper end of town is much more populated than this part. B: Maybe we should live here since there is less traffic. upper a. 上面的，上部的，较高的 A: If you sit upright it would help your posture and give you less back pain. B: Thanks. I’ll give it a try. upright a. 1。直立的，竖立的，垂直的；2。正直的，诚实的 ad. 挺直着，竖立着 A: I am very upset that you left the dishes unwashed.