an unusual or odd habit, behavior, or interest

extreme pickiness or intolerance for moral, social, or professional imperfection

one's strong personal passion, obsession, or particular habit

A euphemism for male homosexuality, originating from a story about Emperor Ai of Han cutting off his sleeve to avoid waking his sleeping lover, Dong Xian.

pica (medical condition involving the consumption of non-nutritive substances)

the psychological condition or behavior of indecently exposing one's genitals in public

a bad habit

sadism (fetish)

addiction; a deep-seated habit

to have strange and eccentric addictions or tastes (idiom)

sexual interest in feet

onychophagia (nail biting)

sexual fetish

an obsessive fondness for books; bibliomania-like habit of collecting/reading books