A buff is someone who has a strong, special interest in something.

VOA: special.2009.05.17

Now we are about to come upon Ramadan, and are you planning anything special for yourself and for the students at Princeton? What's your hope for someone who's about to embark on Ramadan, and Muslim who's in your care?

我们马上就要过赖买丹月了，你为你自己,和普林斯顿的学生准备了什么呢？,你希望那些要开始斋戒的人和，你的学生做些什么呢？

普林斯顿公开课 - 人性课程节选

"Don't keep them away from something that can change their lives and give them a new vision and give their parents a new vision of them, just because they don't want someone in the community to say, 'oh,your child is special."

VOA: special.2009.08.23

But to be chosen by your peers, especially someone like me who has been to four Olympics, who grew up in Lake Placid , it's pretty special to be recognized in that capacity."

VOA: standard.2010.02.27