noun: (medicine) Initialism of postmenopausal osteoporosis.
noun: (slang) Initialism of pornography, masturbation, orgasm. [The explicit literary or visual depiction of sexual subject matter; any display of material of an erotic nature.]
noun: (business) Initialism of project management office.
noun: (government, Canada, Australia) Initialism of Prime Minister's Office; The Office of the Prime Minister, composed of the prime minister and his or her top political staff.