Is MARTS a Wordle Word?

Yes. MARTS 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 MARTS mean?

A license to pass the limits of a jurisdiction, or boundary of a country, for the purpose of making reprisals; a letter of marque.
A brand or make of a manufactured product, especially of a motor car (in contradistinction to a model).
A ship commissioned for making captures.

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

Starter word rating: AverageIn the top 14% of all valid Wordle words for testing common letters.
Vowels: A
Unique letters: 5 of 5
Common letters: A, R, T

Hard-mode trap: 9 valid words fit the pattern _ARTS. 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.