Similar to a Surrogate, this is the female that was not intially good enough to have a mans child, but because she is so expendable, she is now used as a spare part to conceive a child.
The chick i wanted to be my baby mama aint havin it, some im bout to hit up Tonya, she gon be my spare-agate baby mama...
by TJ Goats December 24, 2011