Is RULES a Wordle Word?

Yes. RULES is a valid Wordle word.

It is not on the Wordle answer list, so it is unlikely to be a daily answer.

Plurals ending in S are almost never chosen as Wordle answers.

What does RULES mean?

/ˈɹuːlz/

A regulation, law, guideline.“All participants must adhere to the rules.”
A ruler; device for measuring, a straightedge, a measure.
A straight line (continuous mark, as made by a pen or the like), especially one lying across a paper as a guide for writing.

7 more noun definitions

A regulating principle.
The act of ruling; administration of law; government; empire; authority; control.
A normal condition or state of affairs.“As a rule, our senior editors are serious-minded.”
Conduct; behaviour.
An order regulating the practice of the courts, or an order made between parties to an action or a suit.
A determinate method prescribed for performing any operation and producing a certain result.“a rule for extracting the cube root”
A thin plate of brass or other metal, of the same height as the type, and used for printing lines, as between columns on the same page, or in tabular work.

2 more verb definitions

To decide judicially.
To establish or settle by, or as by, a rule; to fix by universal or general consent, or by common practice.

Definition from Wiktionary, available under the CC BY-SA license.

Starter word rating: GoodIn the top 5% of all valid Wordle words for testing common letters.
Vowels: U, E
Unique letters: 5 of 5
Common letters: R, L, E

Hard-mode trap: 8 valid words fit the pattern _ULES. If you reach it, you may need several guesses to find the last letter.

Letter ratings use how often each letter appears in Wordle answers.

Tap its tiles to the colours Wordle showed, and the Wordle Solver lists every word that still fits, with the best next guess.