When someone has anal sex with some ugly bitch and she sucks his dick right after. Later her and some other guy hook up and he kisses her poopy dick mouth, thusly receiving the poop dick mouth.
Puffins are more prone to poop dick mouth than most other animals.
Noun: an insignificant, loud-mouth, jerk-off who totally fucks himself over every time he opens his big fucking mouth. To be more specific, someone who repeatedly slaps themselves in their own face with their own proverbial cock while at the same time ejaculating into their own eye socket, causing irritation not only to themselves, but also to everyone around them as well.
Example 1: "Don't be a dick mouth!"
Example 2: "What a dick mouth!"
Example 3: "Congratulations-you are not only stupid, but are also the king of all dick mouths!"