A woman that is generally known for lying and taking advantage of men. The origin of this specific definition comes from an old wives' tale about a young woman who is persecuted and inevitably beaten for her promiscuous behavior in the early 16th century, after sleeping with a group of men and giving them an illness without any known cure at the time.
John: I don't get it man, Lauren dumped me the other day and I don't know what I did wrong.
Jim: She's fucking other guys man, she's just a donnelly. You'll find better.