It's very well defined. The term has been used for hundreds of years to refer to specific political attitudes. It was made meaningless by the American political machine, purposefully.

Do an ounce of research and you'll find three closely related definitions used by Marxists here:

https://www.marxists.org/glossary/terms/l/i.htm

Marxism is a political science. It is precise. That is one of it's many strengths.