What is "Wash"

Just to mention again, I'm a newbie, so apologies for what is probably a "Detecting 101" question.

The last couple of videos I've watched has both guys digging for a target on open ground and making comments like "into some good wash" or "not bad wash" as they dig deeper (maybe 6 to 8 inches) below the surface toward their find. What is wash? Is it like bedload sediment from creek or river bottoms?Or is "wash"  the same as wash load? I though wash load was the name given to light particles in the water that were in constant suspension. The material the two diggers were removing appeared to be coarser, heavier material.

Gday Bob,
`wash dirt` or the `wash layer` was a name given by the early diggers to the layer that they washed to recover gold.
This layer usually had either suspended Quartz and Ironstone,angular country rock,rounded pebbles,slate fragments or was a clay layer of a different colour,and this varied greatly from field to field.

Thanks for passing that on, Gus.

I may be wrong, but I thought the guys in the videos had applied the term a little loosley, but then other people have given me different definitions of wash from it being the material that gathers in the dead or slower waters of bends to run off sediment.

Thanks again.

Wash.. oh yeah! ...that is what we do on the last day of a two week long detecting trip, it apparently makes us more attractive to the opposite sex. 

Wayne.