Someone who enjoys pleasing a man by worshipping their balls (see testicles). When properly done both right and left balls are given equal attention as to not make the other jealous. The act of ball kissing can also be used as a method to increase sperm counts for fertility purposes as kissing the balls helps stimulate sperm production and also increases both volume of pre-cum and ejaculations. Not to be confused with a ball licker who is someone that uses pleasure as indirect barter for financial benefit (see brownnose). The method could also be used by a woman right before sexual intercourse with the penis attached to the balls being kissed as a way of improving the performance of the penis that is about to penetrate the vagina.
My girlfriend is such a good ball kisser. She's a real giver when she knows she's gonna get some good sex.