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When you bang a chick while she's on her period and your balls get all "rusty". Not to be confused with red wings which is when you eat a girl out on her period.
I fucked this ho last night and I didn't know she was on the rag til the next morning when I saw my rusty coin purse.
by Classickgirl77 November 26, 2013
To perform oral sex on a women when she is on her period.
Aye yo Bitch! May I use your Rusty Coin Purse?
by PussyAssFiend January 24, 2010