A title commonly used to describe one's heterosexual friend.. It is referring to the fact that if you performed oral sex on a male, the result would be that your breath would emanate the smell of that man's genitalia, thus giving you the breath of a "faggot", or homosexual.
Note: This is usually reserved to be directed towards men, as modifying the adjective to a more aquatic-animal based term would better suit a female.
i.e.) Fish Breath, or see Tuna breath