Does intentionally thinking about sex to arouse one's desires, by a young man in his twenties, fall under the ruling of masturbation?

It is not permissible for an unmarried young man to think or imagine that he is having intercourse with his wife before marriage, because it is a means to commit indecency. However, if the thought of intercourse occurs to a person spontaneously, there is no sin upon him. But if he ejaculates from enjoying this thought, he must perform ghusl (ritual bath). As for intentionally thinking about it and bringing it to mind repeatedly, it is not permissible, because it contradicts the character and chivalry of a Muslim, and it may increase and inflame lust, and it may turn into a firm intention for which one is held accountable. It must be known that most scholars prohibit a man from having intercourse with his wife while imagining another woman.