Sub-fusc is academic dress (http://en.wikipedia.org/wiki/Sub_fusc), which is mandated by university statute for certain events -- including exams. Actually I suppose technically the sub-fusc is the clothing that is not academic dress, which would make the cap and gown (and hood, for those who have them) 'fusc', if you see what I mean. But, whatever. I'm not actually opposed to sub-fusc -- there was a student referendum recently on the question of eliminating the requirement to wear sub-fusc at exams, and the majority was overwhelming in favor of keeping it -- but, but, too hot.