rag week

From rag (“university students society run for charitable fundraising”) +‎ week, possibly from the verb rag (“tease; torment; banter”).

rag week (plural rag weeks)

1. (chiefly Britain and Ireland, university slang) An annual event in many universities where students engage in unusual activities to raise money for charity.
   • 1949 April, The Texas Outlook, volume 33, number 4, page 4:

     This week has been the University College Rag Week. The students are given more or less a free hand all the week. They organize a series of revels culminating in a grand procession and collection this afternoon.

   • 1982 January 6, B.A. Young, The Financial Times, section 1, page 9:

     The only acting that looks like anything but rag week at a bad university is by Billy Hartman as a private detective.

   • 1987, Terry Pratchett, Mort, page 222:

     Worse than that, too, during Rag Week when the drink flowed quickly and the privy seemes too far to stagger.

   • 2002 December 19, John Thaxter, “Tower of Bagel”, in The Stage, page 15:

     In truth the gags seldom rise above the level of an undergraduate Rag Week but speed, quickchange wigs and sheer chutzpah from Russell Bentley, pretty blonde Marianne Levy, Joel Brookes and Teddy Lawrence give wicked twists to such as 'Richard and Judaism', a Who Wants to be a Millionaire? contestant whose phone-a-friend is his argumentative Jewish mother, a wondering 'Wandering Jew' and a savage Shylock rehearsal scene.

• rag day

• Rag (student society) on Wikipedia.Wikipedia

From rag (“piece of old cloth”) +‎ week. From the former use, by women, of rags to protect their clothing from menstrual blood.

rag week (plural rag weeks)

1. (British slang, vulgar) The days of the month when a woman has her period.

   I wouldn't bother trying to get off with her – it's rag week.

• menstrual period, monthly friend, monthly visitor