Masturbation means to arouse yourself sexually, usually to orgasm. Other expressions for masturbation are 'to jerk off' for males or 'to finger oneself' for females. An old and very negative term is 'self-abuse'.
Another word is onanism.

This word is derived from Onan, a character from the Old Testament who was punished by God because he 'spilled his seed on the ground'. The true reason for Onan's punishment was that he did not want to get his deceased brother's widow pregnant, something he had been ordered to do on the basis of what was customary in those days.

In nineteenth-century Europe the fear of masturbation increased and reached a high point in the early half of the twentieth century. In order to scare off adolescents it was said that masturbation resulted in self-contamination, led to tuberculosis of the spinal cord, and could cause meningitis and insanity.

On top of all that, small devices were invented that 'responsible' parents could tie around a boy's genitals to prevent 'the wickedness' to develop. Some of these devices were equipped with stings or shrewd alarm devices that would cause pain when the boy had an erection and warned the parents.

Also, the clitorises of thousands of young girls who were suspected of masturbation were removed surgically.
It comes as no surprise that all this intimidation reduced the joy of living and led to fear, guilt, and feelings of inferiority and self-contempt. That was the fate of numerous people who could not refrain from masturbation in spite of all the fearful prospects.

Of course, a majority practised it without a great deal of individual suffering: they just kept the practice secret, and felt that at least they were not as bad as the 'real' masturbators who ended up in the law courts or the psychiatrist's consultation room, and were said to be 'obsessed' or 'addicted' because they practised self abuse several times a day or used perverse stimulans like 'obscene' pictures.

Sexologists and educators of the second half of the twentieth century gradually changed the thinking about masturbation. At present the majority agree that masturbation is not harmful, but even rather a healthy sexual activity. Still, many people feel uncomfortable about the practice, do not condone it in young children, priests or married people, and see it as additional evidence in cases where someone is accused of some moral offence.

Research has shown that most people masturbate every now and then. It used to be thought that boys masturbate more often than girls, presumably because they discover their penis at a relatively early age since they pee with it. That is not true. Most people masturbate before they become twelve. This does not mean that someone who starts later is not normal.