To an extent, it means what the user implies it means. To take a specific example, think of the largest most well-known social media website. There is a huge amount of data contained within one single entity. And the specific thing here is turning those data into information. Knowing a few facts about "John Smith in Milwaukee" might be useful to his friends and a few marketeers. Knowing about his peer group, about typical Milwaukians, his age group, people called Smith etc. Etc. Is likely to be much more useful to big organisations.
There are obviously thousands of other instances in ****book alone. Add census information to it, demographics etc. And you have really big and complex data.