Grinding something by hand in a mortar (useful with a pestle inserted: 干). BREAK APART refers to grinding with a pestle, and, the initial insertion into the mortar (see 臼) the meat mincer, that cavity with two sets of lips「peaked with clitoris」「using stone pestle while turgid, beating by hand.」Concept of「snowy pure whiteness」as unsoiled, not yet dirtied by others, untouched by [other] human hands, virgin white as in virgin wool from a ewe lamb, not surrounded by any black hairs yet, and so on. There are at least 15 English definitions of「mill, milling」that refer to using a tool to reshape something, grinding, performing a mechanical operation or function, moving slowly back and forth, or to beat and stir into a froth (that might also account for the snowy stuff already mentioned—none of the staff will admit to anything).
「Rocks with clitoral glans」as POUNDING AGAINST WOOL after the appearance of copious vaginal froth on the surrounding fringes of the vagina, labia, and the penis: during ovulation of a female human and estrus of other animals such as sheep, the individual can become more sexually aroused than at any other time. Adding a dildo and/or an actual penis with enthusiastic action acts just like a kitchen whisk with frothy white discharges whipped up and resembling egg white meringue, mousse, cotton tufts and tassels, or sheep wool, and when observed causes great excitement. Froth is pumped out spurting from the vaginal orifice about once per second as the muscles contract and release during successive waves of orgasm, forming what appears to be virgin sheep wool surrounding the quivering orifice.
「As a woman's cycle progresses, the mucus secreted from the cervix will change due to hormonal fluctuations. A woman is considered to be ovulating and fertile when the mucus is clear, stretchy and slippery, and looks like egg whites.」
[ https://ic.steadyhealth.com/most-fertile-cervical-mucus 2017-05-03 ]
「Understandably this 'foaming at the mouth' phenomenon has your nerves on edge. But, if you were recently tested for sexually transmitted infections (STIs) and received a clean bill-of-health, most likely the foam-like substance is just a result of the combination of two art forms: The Joy of Sex and The Joy of Cooking. The main ingredient here would be semen…. Semen is loaded with protein, a pinch of sugar, and a dash of salt. The dildo and your boyfriend's enthusiastic 'mixing' inside of you acted just like a kitchen whisk.」
[ https://goaskalice.columbia.edu/answered-questions/foaming-after-sex/ 2017-05-03 ]

External source definitions …excluding politically incorrect concepts and other meanings deemed offensive today; may include extended definitions, euphemisms, and mnemonics)
Chinese: mill; see 磑磑|硙硙; snowy white; pure white; spotless
Japanese EDRDG: mortar, hand mill
Unihan extended: stone mill; grind; break apart