G'day
I reckon the word patch could pretty much cover any spot that produces more than one nugget, because every patch either small or large that I have found has started with finding the first nugget (the indicator) and then when I get a second or third nugget close by I know that there is possibly even more, then you need to change tactics to really work the spot and see what else could be hiding there by using bigger and smaller coils to really cover the area, some patches will be very compact and others very wide spread so don't be scared to spend the time to cover lots of ground around the area as well
Some other terminology
If you find a single piece on open ground and don't find another nearby we reckon it just fell out of an Emu's bum
A very small nugget is a Bee's D**k
Anything over a gram "A Clunker"
cheers
stayyerAU