I had to add an explanation because all the definitions I've seen here are inaccurate. Broad refers to the distance between the vagina lips of the human female. When the distance becomes wider than normal due to wear and tear, high mileage and rough use a woman becomes a broad. A broad is not necessarily a slut because all the wear and tear may have come from one man but a slut is always a broad.
Steve: Hey Joe is Lisa a good lay?
Joe: No man she's such a broad, I couldn't get myself to ejaculate in her.