The fishy smell one obtains in their mouth when they have been eating a plethora of poon.
Can be used to insult someone, or used as a word for "good" like "sick" or "dope".
(side note: eating tuna is a risk)
"Charlene, I think your boyfriend has been cheating on you! He's got a real bad case of the Poon Breath."
"Oh no that's just because he had been eating tuna"
"Oh. That'll be it."
"Hey Lester, you're such a Poon Breath!"
"Duuuuude, that is SO Poon Breath" *thumbs up*