The hairy pubic area of a man, or sometimes disgustingly, a woman. What makes it a beard is the shape or pattern in which the pubic hairs grow (from under the bellybutton to the grendel).
Beards refer to the typical appearance of scifi nerds, star trek nerds, anime nerds... fat, piggy-eyed, giant, unkept beard, bottle-lens glasses, star trek uniforms, wheezy, asthmatic, etc. So, when someone refers to a beard, they are referring to some form of nerdy discussion, the longer the beard, the more knowledgable the person is typically being.
The structural resemblance a female and male share. The lower half of the body near the inside of the legs is recognized as the beard of the woman, while men tipically present their bear openly near the mouth and nose of the face.