Similar to Jackson's Mustache and Hamilton's Mustache, Jefferson's Anus is when, the morning after you have sex, but before she wakes up, you cum on the girls asshole and jam a nickel in. This is usually for cab fare. This is only practiced by truly douchey dickbags.
X: Hey man, how did that chick get home?
Douchey Dickbag: I don't know, brah, but I gave her Jefferson's Anus when I got up! Pound it!