Everyone masturbates differently: some use their hands, some use vibrators, some can simply rub their legs together and some like to hump a pillow. Pillow humping is, well, humping a pillow. So how can it be hard? You place a pillow between your legs and rock your hips to achieve the grinding sensation against your clitoris that so many women love. Often women start humping their pillow without even knowing what a clitoris is no thanks to shoddy sex education ; they just know that it feels good. Place the pillow you want to hump between your legs while you lie face down on the bed.