celibacy. Celibacy is obligatory for all members of the Saṃgha. Sex is regarded as a powerful bond to the mundane (laukika) world and not appropriate for one who has renounced home and family. Since Buddhism regards craving (tṛṣṇā) as the cause of suffering (duḥkha), the dangers of sexual desire are obvious, and are frequently pointed out in Buddhist literature. There are strict penalties in the Vinaya or monastic code for monks and nuns who fail to remain celibate. The first of the four pārājika-dharmas prohibits sexual intercourse, and the penalty for breaking it is lifelong expulsion from the Order. More minor offences, such as masturbation or lewd conduct, reported in the Vinaya, are punished less severely. Married lay-people may also adopt the practice of voluntary celibacy for longer or shorter periods.

A Dictionary of Buddhism, Oxford University Press, 2003, 2004 (which is available in electronic version from answer.com)

celibacy : (f.) brahmacariyā. (nt.) avivāhakatta. 

A.P. Buddhadatta Mahathera, Concise Pali-English and English-Pali Dictionary [available as digital version from Metta Net, Sri Lanka]