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The single mom discount is when a single mother (preferably a MILF) doesn't want to pay full price for something so she seduces the man/women into sexual activity to cover the price.
Plumber: "Alright, ma'am your sink is all fixed, that will be $189"

Single mom: "Oh my, that's a little high, can I have the single mom discount?"

Plumber: "The what?"

Single mom: *Starts to stroke plumbers cock*

Plumber: "Ohh yeaa that feels nice"

...The Single mom and the plumber engage in sexual activity for about an hour...

Plumber: *Putting his clothes back on* "Well ma'am, your grand total comes to $15"

Single mom: "Now that sounds reasonable!"
by LeftHandMan October 18, 2009