Top Definition
Fetus Spiders occur when a person takes part in sexual intercourse just as they, or their partner, enter their menstrual cycle. It is quite the feat because you have to time your cum shot just right so you can fertilize the egg as it's exiting through the beef curtains. Once fertilized, the Fetus Spiders become larva and nest within both partners pubic forests. It takes, on average, one month for a feti-larva to become a full grown Fetus Spider. Once in Fetus Spider form, the creature is able to crawl and reproduce, just as everything else.
They average to be about 50-60 pounds, can run up to 85 mph and stand 5-7ft tall.
Works best while doing it doggie style or reverse cowgirl, although scientists have not proven this to be true.
1. My girlfriend breeds the best Fetus Spiders in her raunchy vagina.

2. A Fetus Spider reproduced with my baby and made feti-larva in my ball fro.

by vagrant48 March 09, 2009

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