The sweat right between a mans testicle sac and leg that has condensed and gathered lint, hair, dirt etc... Usually the stinkiest/manliest part of the mans body. Although it is gross, women will always be attracted to it.
Oh, Billy's DuckButter smells so strong! I just want to spread it all over my toast!
A game that begins with eating a tremendous amount of greasy duck meat with your partner. After you both have had your fill, strip naked and begin having really rough sex. The first person to shit loses.
I had a really rough Christmas, but at least I beat Heather at Duck 'N Fuck. That bitch shit all over the floor!