Is FOURS a Wordle Word?

Yes. FOURS 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 FOURS mean?

The digit or figure 4; an occurrence thereof.
Anything measuring four units, as length.“Do you have any more fours? I want to make this a little taller.”
A person who is four years old.“I'll take the threes, fours and fives and go to the playground.”

4 more noun definitions

An event in which the batsmen run four times between the wickets or, more often, a batsman hits a ball which bounces on the ground before passing over a boundary, resulting in an award of 4 runs for the batting team. If the ball does not bounce before passing over the boundary, a six is awarded instead.
A power forward.
Four-man sweep racing shell, with or without a coxswain.
A four-pennyworth of spirits.

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

Starter word rating: WeakIn the top 47% of all valid Wordle words for testing common letters.
Vowels: O, U
Unique letters: 5 of 5
Common letters: O, R

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