Purity: Movement of Semen without Ejaculation

Practical Laws of Islam as per the teachings of Ayatullah Sistani

Ruling 351:

If a person feels the movement of semen but does not ejaculate, or if one doubts whether semen has been ejaculated or not, ghusl is not obligatory for him.

-Ayatullah Sistani, Practical Laws of Islam, Purification (Taharah)