a person that is stupid, retarded, or just plain ignorant; a combination of a dumbass and a shithead; also known as an asshead
kyle: yesturday my little brothervan was playing videogames while jacking off and he squirted himself in the eye
jack: wow! your brother's such a dumb shit
A dumb shit is a type of person who harbors questionnable political ideals and expresses it using mugs with urban dictionary definitions written on them.
Mittato is such a dumb shit. His mug has like 5 racial slurs on it!