disappearance, fade, vanishing.
In the middle of the lake lay what was left of a disappearing
John himself, who had not been prepared to see them run off from him at the last moment, beheld their active little legs disappearing
as they got over the low ledge of the open window.
It was a long street, and the couple separated before he reached them, the man disappearing
round the corner, while the lady advanced steadily towards himself.