The meaning of the clay of lunacy

The one who slanders a believing man or a believing woman with what is not in them, Allah, Exalted and Glorious is He, will detain him on the Day of Resurrection in a clay of lunacy until he leaves what he said: I said:…

I said: And what is the clay of lunacy? He said: A pus that comes out from the genitals of adulteresses.