Of course there is. :)
You asked how to delete it from the world, not a chunk of the map.
Painting over doesn't remove it, it just thins it out a little... You have to remove it from that chunk if you still want to use the paint in another chunk.
Use the layer options in terrain paint. With the Visualize layer option ticked the chunk will show black/white if there is any terrain paint you have clicked active.
Having the Color Option to 0 means it will erase the paint. Any higher will add that much paint to the map.
https://i.imgur.com/aj75RWo.jpg
The Individual Layer Mode will not show black/white but will add/remove the terrain paint from that layer without messing with the layers above it. ... :)