What does 牛逼 mean? Can anyone define it? What does 牛逼 
 mean?  Someone gave a presentation on it in my school.

Can someone define it?
This word has a very vulgar origin. It literally means cow's sex organ. Paradoxically, I hear it spoken more often among professionals like doctors and professors among themselves. Professional women swear more, and thus speak of it more often.

牛逼


Thriving and formidable. 哈佛是所很 ~ 的大学. Harvard is a thriving and formidable university.
Arrogant, insolent. 没有人敢在那里 ~.  No one dare to be insolent in there. 


牛, cow

逼, 屄, female sex organ.

Source: http://baike.baidu.com/view/54728.htm