rag week

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun UK An annual event in many (mainly British) universities where students engage in unusual activities to raise money for charity.
• noun vulgar, British slang, from the former use by women of rags to protect their clothing from menstrual blood The days of the month when a woman has her period.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun a week at British universities during which side-shows and processions of floats are organized to raise money for charities