A male's “zivah” discharge is usually a sign of a particular internal ailment, and some say, it is a spiritual disease, just like a “metzorah” – leper – was a spiritual ailment. However, occasionally it can be caused by one of the seven conditions: food, drink, carrying a load, jumping, illness, or a sight or thought of a woman.
Rav Huna said that even when it is caused by a stimuli, it has all the laws of a regular zivah, and causes one to be ritually impure, just like semen emission, based on the Torah phrase, “This is the law concerning the zav and one from whom semen was emitted.” Rav Huna's opinion is challenged with four different challenges, but he successfully answers all.
So how is zivah defined? Rav Huna gives the criteria: it is similar in consistency to water of barley dough; it issues from a limp organ, whereas semen issues from an erect one; it is runny and resembles the white of a spoiled egg, whereas semen is viscous and resembles the stark white of an unspoiled egg.
Art: Gilbert Gaul - Man Carrying Sticks at Dusk