At a college or university, the process of removing freshmen and other rookies from a difficult but popular major field. Usually, this means Fs. Lots of them.

Some departments prefer to do the dirty work themselves - stupid required classes that grade on a very steep scale are good for this. Lots, though, prefer to farm out the bloodletting to others - an engineering department might let the physics department take out a good chunk of students, computer science might require a totally useless mathematics course with a high failure rate, etc.