1. The act of not doing something; refraining from: drinking, drugs, sex, etc. Anything really.

2. Sexual abstinence is when someone involuntarily OR voluntarily does not have sex of any kind. This can be due to religious beliefs or for other reasons such as birth control. Sometimes someone practices abstinence on a short term level, others on long term levels. Short term can be during periods, during ovulation so as not to get pregnant, other times it is because a person just can't get laid. Monks, priests, and nuns take vows to remain abstinent, which is a permanent choice.