A bone in the penis (penis bone, boner) usually found in most mammals, like dogs, cats, and walruses. Humans do not have a baculum(erections are caused by blood flow); but girls have the the analogous equivalent- a Clitorus.

In other words, it's the actual missing boner taken from Adam's penis to make Eve(Hebrew doesn't have a word for penis, so they used rib), and the area where God closed the flesh up is the perineal raphe.

Slang- An erection so hard, long, and everlasting like priapism(but not as long or fatal), that it's mistaken for an actual bone grown in the penis.
Ah crap, I couldn't stop thinking about that all-night threesome that I had last night, and my penis grew a baculum.
by Ryuseiken September 21, 2006
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1. A bone, taken from raccoons before roasting, that is used by country folk as a tooth pick.

2. A bone present in most placental mammals, though not in humans, that is used to achieve or maintain an erection.
That hick sat there picking his teeth with a baculum.
by vanishingly February 28, 2021
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The name for the bone found in most mammalian penises. Ironically, humans do not possess a baculum yet we refer to an erect penis as a boner.
Jesse's erection was so prolonged that he might as well call it a baculum.
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