A Brazilian Tuck is when a gentleman places his genitals behind his thighs and appears to have no genitalia.
Did you see Bobby last night? He got so black out drunk he was streaking and even performed a Brazilian Tuck in front of the whole party.
It's when someone inserts their own penis into their own butthole.
Jerry: Yo, i don't have any clean undies so I Brazilian Tucked, is that gay?
Tom: No.