Cofrinho
1
Buttcrack.
There are jokes on this too, because cofrinho is also how we call piggy banks. So when someone sleeps on his chair and you spot his/her cofrinho, some people drop coins in there.
You can either say “mostrar o cofrinho” (show the buttcrack), or “pagar cofrinho” (pay? buttcrack). Both expressions mean that you are displaying your buttcrack.