How do you define a "casual" & "hardcore"?

The terms "casual" and "hardcore" are bandied about in a number of threads, but I am interested in what you all actually mean and think when you say you or another player is a "casual" or "hardcore".

For instance, many people correlate the time you play the game to whether your are "hardcore" or "casual".

Others say that it is how seriously one takes the game.

For some, it is the effort invested or specific aspects of the game that are enjoyed.

How do you define it?

Edit: Grammar >_<