Refers to abstaining from sexual activity, often in a religious or moral context. A formal, somewhat technical term.
Monks take a vow of celibacy.
Chastity is considered a virtue in many religions.
Compound of 不 (not) and 淫 (lewdness, sexual excess), literally meaning 'not lewd'. The exact historical derivation is uncertain; the spelling is conventionally associated with the meaning of celibacy or chastity.