chastity belt

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A lockable device designed to prevent a person from having sexual intercourse or engaging in masturbation.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun A belt-like garment, designed to be worn over the genitals and locked to prevent sexual intercourse, typically for long periods of time, to maintain chastity, or to enforce BDSM submission.
• noun figuratively For a woman, refusal to have sex.