The "2 girls" are two lesbian lovers. "1 cup" is when one of the girls actually poops in the cup. The video continues on with the two girls eating the cup of feces and rolling it in their mouth and making out with the feces in their mouth. The video continues with both of the girl sticking fingers down their throats and vomiting on the feces and on each others face. The video ends with feces/puke all over their faces and mouth.
The video is one minute long. They are not recommend for those who are under 18, easily offended, or have a weak stomach because it is known one of the most disgusting videos to spread across the web.
YouTube has numerous of reaction videos on the net and Family Guy also has a moment where Brian Griffin records Stewie Griffin's reaction. The reaction videos can tell you how gross it is. I, myself, watched it because a friend showed it to me. And I was shocked, but didn't feel sick. But I cannot look at chocolate ice cream the same way again. Let's just hope that two men never do that.
Douche 2: No, I haven... OH DEAR GOD THAT IS FUCKEN SICK!!!
"-hey, have u seen this video called 2girls1cup ? you should check it out, its hilarious
-ok, ill google it tonite"
"-you motherfucker! that link you sent me was the nastiest shit ive ever seen
-oh, 2 girls 1 cup ? lol"