An insult implying that a person has recently had oral sex with an unclean partner. Smegma, being most generally considered as affecting men, when associated with smelling it on the breath also implies homosexuality when this insult is directed at a male.
"Hey smeg breath, quit goofing around and hand me the pliers!"

"Cheryl is such a slut, the boys have started calling her Smeg Breath behind her back."
by Rexomaticus McManus November 28, 2006
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