By dobbing do you mean trading ?
I play in running on horse racing, not a term I've ever heard.
The timeform results section on betfair gives you In running high and lows, I'm not familiar with anyone else who produces the data.
Yeah it's the specific type of trading where you back the horse and then lay it for double the amount at half the original decimal odds price. I.e. back a horse for a £100 at 10.00 and then lay it for £200 at 5.0 to win £100 - exchange comission . I guess you could vary it to something like 25% as you're more likely to get that kind of price movement than 50%.
I think its meant to stand for Double or bust. I was interested to see how many horses actually shorten in price that much and if there were any tools to help identify which horses are more likely to have their odds reduce in play.