A nonsense insult, inspired, I guess by felch. If any meaning is to be derived from it, I would assume that it is implying that the person in question resembles in some way an anus-full of semen, ,ready to be orally incorporated.
Given the kind of people I usually have cause to say this to, that's quite an apt description.
"Golly, you really are one almighty felchbox!"
by Stooo March 21, 2003
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