I'm not sure if this is the right place to ask, but I want to know what the phrase "umbrella revolution" means. This the the context that the phrase occurred in:
An umbrella revolution is swelling outside of the main tally centre at Dewan Suarah (Suarah Hall), with 200 people standing in the rain to show their support for [Democratic Action Party]'s Wong Ho Leng. Around 200 cops estimated in area, but no untoward incidents so far.
It is part of a live report covering a recent election process in a city.
I've Googled and found many references to the phrase 'umbrella revolution', but no definitions. I've checked several online dictionaries, including OneLook, The Free Dictionary, Babylon, and even Urban Dictionary, but there are no definitions. Was this merely an odd expression chosen by the journalist, or does it have any meanings that I am unaware of?