What is the thick white fluid, resembling semen, that sometimes exits during defecation without desire, and what is the ruling concerning underwear soiled by it, and does it necessitate ghusl?

The thick white fluid that often exits after urination is "wady," and its ruling is the same as urine in that it nullifies ablution and is impure. Therefore, the place it has touched on the garment or body must be washed, and ghusl (ritual bath) is not required upon its exit.