A baby born whilst her/his mother is on her period. Thus, when s/he is born, she is covered in blood. The effect is especially pronounced on children born to women with heavy flows.
Nurse: "Oh my God, she's birthed Satan!"

Doctor: "Calm down, that's just a blood baby."
by GoonGoblin8 October 16, 2010
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When something is so absurd that the only way of describing it is to relate it to a baby covered in bloody anal beads.
"Ryan you see that ginormous fucking chick over there... 'yah,'... that's one fucked up blood baby dude!"
by Farkmaster April 13, 2010
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When a girl is on her period, she is said to be having her "blood baby"
"When is your blood baby due?" is like asking her when she is going to have her period.
by AwesomEricc June 4, 2011
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When you shit small bloody turds after taking it up the ass
"Ohh I must've taken it hard pretty last night, I'm spurting blood babys like there's no tomorrow"
by A Corpse October 11, 2005
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When your period is so heavy you can feel it coming out of your vag. It feels like a bucket.

Can also describe the moment when your 'cherry pops' during a womens first time in sex.
'Any one got any tampons &some feminax? I'm having a blood baby'
'When I popped her cherry, she had a blood baby on my mums bed'
by willylyker. March 27, 2012
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The feeling when you stand up on your period and all the blood rushes out of you, feeling like you just gave birth to a baby made of blood.
Dude, I just stood up after taking a nap and I had the biggest blood baby, it was ridiculous.
by GrogieSnople September 22, 2019
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