The original meaning of the word was a muscular man who was more skilled with his fists than his mind. That’s not used much at all anymore.
Much like the complimentary expression “she’s built like a brick shithouse” or the more contemporaneous “thicc,” it seems to have been used ironically, turning an insult about something generally undesirable being excessively over-built on top of its general yuck factor, into praise for how physically desirable a woman is. Sort of, “she looks like she was made by the kind of obsessive perfectionist who’d hire a master mason to put up a field latrine.” Except in this case the connotation of also being kind of dull-witted stuck from the original male definition. But the male bimbo knew what he needed to know: how to use his body to get his way (in his case by pounding the snot out of anyone who got in his way). Likewise, the female bimbo also knows how to use her body to get her way.
So basically the definition should be something along the lines of, “An attractive and curvaceous female who willingly lets herself be used as a sex object, often because it’s her best or only talent.”