Is TRIFF a Wordle Word?

Yes. TRIFF is a valid Wordle word.

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

What does TRIFF mean?

Terrific; wonderful“Our daughter thinks you're wonderful. “Cool” I think was the adjective she used. […] Or maybe it was “triff”.”

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

Starter word rating: WeakIn the top 76% of all valid Wordle words for testing common letters.
Vowels: I
Unique letters: 4 of 5Repeats F
Common letters: T, R, I

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.