People who can't stop having kids and think that having tons of kids is fabulous, AND who think people who have just one child are horrible people for raising "spoiled", "selfish", "socially maladjusted", "lonely" only children (ridiculous stereotype myths in quotation marks). Overbreeders are usually putting those negative stereotypes on well-behaved, well-mannered, calm, happy only children at the same time as they're losing their minds running around in a tizzy trying to rein in their completely out-of-control, fighting hoard of kids.
The overbreeder Duggar family from Arkansas has 16 kids and wants more - scary!
by Martha the Moober June 1, 2006
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A couple who has more than 2.5 biological children. Not to be used to describe families who adopt children, as they are helping the currently over-populated world, not adding to it.

Exemption: A couple who has one child and then becomes pregnant with twins, resulting in a total of three biological children.
"Why can't they come to Zumba?"
"They don't have anyone to watch their kids?"
"Can't they schedule some play dates?"
"They each have four kids!"
"That's what they get for being overbreeders!"
by Wife #2 March 24, 2010
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A practice of selective overbreeding of the high-class elites that can rarely lead to psychological, physical and mental illnesses.
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A practice of selective breeding of the rich people that can rarely lead to psychological, and mental illnesses.
The consequences of societal overbreeding can be catastrophic.
by Slang Advisory Board April 2, 2019
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