In the US, in popular usage, it means someone who supports extensive public programs (education, welfare, research, etc.), even if it means that taxes are higher. It also means someone who is against the government infringing on social freedoms, like equality for people with different sexualities, genders, or races.
The classical usage of "liberal" means someone who supports individual freedom in every sense: lower taxes, fewer government programs, less government spending, and social freedom.
To make it even more confusing, the hard-right of the Republican Party claims to be "liberal" in the classical sense (sometimes also called "libertarian"), but many of them aren't actually libertarian.
And, to make it even more confusing, there are actual libertarians in the US who don't know to describe themselves that way[1][2].
1. http://www.pewresearch.org/fact-tank/2014/08/25/in-search-of...
2. http://fivethirtyeight.com/datalab/there-are-few-libertarian...