解释：

(n.) a person who's annoying because they try to show how clever and knowledgeable they are

一个很讨厌的人，经常炫耀自己的聪明和博学；

(adj.) having an annoying way of trying to seem clever

自以为是的人；

来源：

It is a phrase coined by Red Forman on an episode of That 70's Show. 这个俚语来自于美国一部很著名的情景喜剧“七十年代秀”中的一个人物，这个人叫Red Forman.其中他第一次说道, Nobody likes a smart-ass.

Although Red Foreman did use it well and it was very funny, it probably evolved from the original term "smart alec" 尽管Red Foreman在剧中将这个词组用得很好而且很幽默，但是这个词组很有可能来源于另外一个词，叫做“smart alec”

Hoag was a pimp and a thief in New York City in the 1840s. Partnered with his wife Melinda and another known as “French Jack”, they would rob his wife’s “customers” while she otherwise distracted them. Alec是一个人的名字，全名叫做Alec Hoag，他是一个1840年左右生活在纽约的一个皮条客，和他的妻子一起，通过色诱抢劫顾客的钱财。有时候被抢的顾客会去报警，但是Alec通过买通警察，经常会逃避被处罚，所以当地的警察就会说Don’t be a Smart Alec.后来smart Alec慢慢地演变为smart ass，用以指代自作聪明的人。

这个词组不是很offensive，三颗星是满分的话，那么offensive的程度只有一星。

举例：

1. 王小二是一个自以为是的家伙，总是吹嘘自己上知天文，下知地理，其实他只是略懂皮毛。

He thinks he knows everything but actually he is only a smart ass.

这里做名词来用

2. 经验丰富的种植户总是不喜欢理论派的教授来教自己如何来经营农场，那么就可以将：

We don't need some smart-ass ecology professor coming out here and telling us how to run our farms. 这里做形容词。