I've always liked operational definitions...they are what they do:
Liberals are very intolerant of people who preach tolerance for any opposing idea;
Liberals are people who have a much better idea of how to spend your money than you do (Hmm, children must be liberal);
Liberals are the only people who know how to make the world a better place for everyone, but never look at the results, only the intentions;
Liberals are people who believe only the "government" can solve problems (normally after the "government" creates the problems);
Liberals are against individual rights at any time, for any reason, and in favor of the rights of any politically correct group;
Liberals are firmly against any form of "hate speech", defined as any non-liberal view (see first item--tolerance);
Liberals believe the Constitution has no actual meaning, it may only be understood in terms of the immediate situation at hand (If there is no fixed meaning there is really no meaning at all—only expediency matters).