Professional student refers to a person who receives multiple degrees and keeps taking courses instead of holding a profession related to the degrees earned. It can be a compliment or an insult depending on the speaker.

“专业学生”指的是那种已经拿到好几个学位，依然继续进修深造，而不是去从事和既得学位有关的职业的人。这个称号可能是褒扬，也可能是挖苦，取决于讲话的人。

Ex. 1: a compliment 

"Man, I think you're so cool for writing a dissertation on Mesoamerican maize fertilization. You're a real professional student!" 

“老兄，你写的关于中美洲玉米受精的论文实在是太酷了。你真是个不折不扣的专业学生！”（褒扬）

Ex. 2 an insult

"Hey Jack, won't you get a real job and quit being a professional student?"

“嘿，杰克，你干嘛不去找份真正的工作，老是做专业学生呢？”（挖苦）