What is Maxim?

Legal Definition
term used for the rules and principles that have been accepted and recognised as they are reasonable and fair.
Legal Definition
An established principle or proposition. A principle of law universally admitted, as being a correct statement of the law or as agreeable to natural reason. Coke defines a maxim to be "conclusion of reason," and says that it is so called "quia maxima ejus dignitas et certissima auctoritas, et quod maxime omnibus probetur." Co.. Litt. 11a. He says in another place: "A maxime is a proposition to be of all men confessed and granted without proofe, argument, or discourse." Id. 67a. The maxims of the law, in Latin, French, and English, will be found distributed through this book in their proper alphabst-ical order.
-- Black's Law Dictionary