Fiqh-us-Sunnah Volume 1, Purification and Prayer, Fiqh 1.010.

Wadi is a thick white secretion discharged (by some people) after urination. It is considered impure. ‘Aishah said, “Wadi comes out after urination. The person should wash the private parts and perform ablution. It is not necessary to perform ghusl. This is related by Ibn al-Munzhir. Ibn ‘Abbas related that “mani (sperm) requires ghusl. As for mazhi (semen) and wadi they require a complete purification.” This is related by al-Athram. Al-Baihaqi has it with the wording, “Concerning mazhi (prostatic fluid) and wadi, he said, ‘Wash your sexual organs and perform the same type of ablution as you perform for prayer.”‘