CB is a common abbreviation for a chastity belt or cock cage for men, it is an abbreviation for Chastity Belts, the English translation of chastity belt.

There are chastity belts for men and women. The Dominant usually holds the key to the chastity belt and determines when the chastity belt may be removed. The Dominant has the key and becomes the 'Key Holder' to prevent a sub from having an orgasm, and even an erection can be forbidden. For this you can use a chastity belt. Within a TPE or pure D/s relationship, it also underlines the fact that the sub (and his sexual desires) is the property of the Dominant.