A tank top worn by men to prove their "manliness". Also known as a wife beater.
I was walking down the street the other when I saw some scrawny wannabe ghetto kid wearing a manktop.
a tanktop worn by men, usually gay men
person 1: why are you wearing a manktop, justin?
person 2: you may not have noticed, frank, that i am not straight. plus, it matches perfectly with my manpris and my manbra.