Is DIFFS a Wordle Word?

Yes. DIFFS 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 DIFFS mean?

Any program which compares two files or sets of files and outputs a description of the differences between them.
The output of a diff program. A diff file.
A difficult route.

To run a diff program on (files or items) so as to produce a description of the differences between them, as for a patch file.
To compare two files or other objects, manually or otherwise.

The quality of being different.“You need to learn to be more tolerant of difference.”
A characteristic of something that makes it different from something else.“There are three differences between these two pictures.”
A disagreement or argument.“We have our little differences, but we are firm friends.”

7 more noun definitions

Significant change in or effect on a situation or state.“It just won't make much difference to me.”
The result of a subtraction; sometimes the absolute value of this result.“The difference between 3 and 21 is 18.”
Choice; preference.
An addition to a coat of arms to distinguish two people's bearings which would otherwise be the same. See augmentation and cadency.
The quality or attribute which is added to those of the genus to constitute a species; a differentia.
(logic circuits) A Boolean operation which is TRUE when the two input variables are different but is otherwise FALSE; the XOR operation (\scriptstyle A \overline B + \overline A B).
(relational algebra) the set of elements that are in one set but not another (\scriptstyle A \overline B).

2 more noun definitions

One of two coils of conducting wire so related to one another or to a magnet or armature common to both, that one coil produces polar action contrary to that of the other.
A form of conductor used for dividing and distributing the current to a series of electric lamps so as to maintain equal action in all.

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

Starter word rating: WeakIn the top 95% of all valid Wordle words for testing common letters.
Vowels: I
Unique letters: 4 of 5Repeats F
Common letters: I

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