look up any word, like cleveland steamer:
 
1.
The act of urinating on a woman's head, effectively drenching the hair, and then proceeding to have the woman give the man a blowjob whilst her wet hair is draped in front of her face, ergo dirty curtain.
My girlfriend gave me a dirty curtain last night, and by golly was she wet.
by xXxDolphinClubber69 February 12, 2012