Sandman. This is a direct quote from the site you linked.

What's the difference between bullying, harassment and assault?

Bullying differs from harassment and assault in that the latter can result from a small number of fairly serious incidents - which everybody recognises as harassment or assault - whereas bullying tends to be an accumulation of many small incidents over a long period of time. Each incident tends to be trivial, and on its own and out of context does not constitute an offence or grounds for disciplinary or grievance action.

I don't know why you are disputing your own source.