A girl of the rare variety who - perhaps inexplicably - "inspires love" in a large proportion of the guys she meets. This effect is often partially attributable to beautiful eyes, dimples, a predisposition to smile or genuine friendliness - but these features rarely account for the dramatic difference between the sincerity of her admirers and others'.
Etymology: Thought to derive from "hardy"; any "RD" must be emotionally tough (and slightly stubborn) to deal with the fallout from her warring suitors.
"20 guys declared their undying love for her yesterday, seven of whom she'd never previously spoken to... but she smiled, carried on, and effortlessly resolved the free-for-all that followed as 19 tried to impress her with macho posturing. What an RD."
"Yeah, I've never loved anyone like that before. Messes with your head. No idea what she did to me. Must be an RD."