Is ghusl or only wudu required for prayer when masturbating without ejaculating any semen or sperm?

Masturbation is forbidden. If you feel semen about to exit after engaging in it, and you prevent its exit so that it does not come out at all, then according to most scholars, you are not required to perform ghusl (ritual bath), unlike the well-known opinion of Ahmad, who holds that ghusl is obligatory. The argument for not requiring it is that the Prophet (peace be upon him) made ghusl dependent on seeing the semen and its gushing forth. However, if semen does exit, even after a period following masturbation, then ghusl becomes obligatory for you.