1. Technically, someone who falls to the left in a political system, who believes in government programs (healthcare is a good example, as is welfare) and a larger scope of government, also favors monitoring of business and protection of constitutional rights. Someone who believes that the federal government should have more importance than state government,
2. Somehow, it has turned into an insult, like the word conservative. Usually used as such by people who have never taken a political science class and don't know what the word means. Often used to describe "liberal media" despite the fact that most media outlets are owned by conservative corporations like ClearChannel, and the prevalence of conservative talk shows.
1. "He has a liberal attitude towards life"
2. "That gay homo is a liberal comunnisst pinnko! Limbaugh toled me so, and O'reailly agreez! Fox News Rulz, they so impartial in their support of everything Bush! Goddamn liberal media!