To go down on (felate) your mate's (friend's) girlfriend or recently ex girlfriend.
(in that he may have consumed some of your semen).
You went down on my ex?
You're a porridge muncher!
You munched my porridge, ah ha. Porridge muncher.

Or
He went down on your girl?
What a porridge muncher.
by XSorXpire September 7, 2006
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