「Person sitting on buttocks, genitals」is someone refusing to cooperate, perhaps with arms folded across the breasts and tight-lipped, too. Figuratively, anyone who remains in that position is refusing to allow access to the buttocks or genitals, in other words, refuses offers of sex, such as a PRIESTESS, Buddhist NUN, or some other BITCH (when not in heat)…everyone knows that the imperturbation of most any woman can exceed that of men, and most especially someone BITCHY (see 鬼). Cooperation would likely entail crouching on all fours, instead of sitting on her buttocks. Perhaps it refers to a woman's degree of cooperation or lack thereof during sex, with the coital action becoming necrophilia-like, penetrating someone cold and hard, frigid, unfeeling and not moving, cold, lifeless and just「sitting like a corpse.」
　Conversely and more likely, elements as the「genitals of a concubine, sitting person with no-longer-integrated feet」may refer to female canids, or BITCHES in heat that can be extremely cooperative and horny while copulating with one dog after another nonstop, not unlike the「genitals, buttocks of a concubine」as a「horny bitch in heat.」Suggests allowing access to the anal orifice (the「buttocks」尸) but not the vaginal orifice, particularly in light of the many glyphs depicting Buddhist males (formerly, Tibetans) as 'buttfuckers'…could be, recalling that the Taoist sages who created these glyphs held no great affection for religion in general and Buddhists in particular. As a FEMALE SERVING IN A RELIGIOUS OR DIVINE ROLE, recall that shamans originated foot-dis-integrating of apprenticing girls, transforming their feet into artificial genitals so that the girl could service many dogs, often simultaneously and one after another nonstop, generating revenue for the shaman's temple or shrine.

Modern definitions (that generally disregard history) …excluding politically incorrect concepts and other meanings deemed offensive today; may list only pigeonholed definitions, euphemisms, or meaningless mnemonics)
Chinese: Buddhist nun; (often used in phonetic spellings)
Japanese: nun, bitch, Amagasaki, Hyogo, bhikkhuni, native of Amagasaki
Unihan extended: Buddhist nun; transliteration
EDRDG: nun