Top definition. Every guy may have his specific girl-next-door prototype, but in general, she's the girl whom you always admired from afar and were afraid to approach, fearing that any erotic projection toward her would ruin her image as a decent, pure and almost virginal womanly ideal. She's in your mind at least untrodden ground; unspoiled by other men and so sweet-natured it almost frightens you to think of her in explicit sexual situations. Here's another example: Picture your sister's best friend from when you were kids.