The definition of the terms are even more subjective than what you describe. The Conservative Party of Canada is a little bit to the political left of the United States' Democratic Party.
To answer your question, usually social scientists and pollsters let people describe themselves as liberal or conservatives. Do the same: if you need to you talk about liberals, moderates, or conservatives, be clear you talk about people who self-describe as such. Also mention the country you're talking about. A very large segment of the site's population come from outside of the United States. Take a look at the top usersthe top users and you'll see what I mean. This is not an American website.
I have an even better advice, though: don't use those terms. If you need to describe the group that espouse a belief, you're most likely (but not necessarily) doing it wrong. You don't need to say "liberals are more likely to support minimum wage" to ask whether increasing the minimum wage increase unemploymentwhether increasing the minimum wage increase unemployment. Most questions are about facts, not affiliations.
