[Gryphin]

According to Merriam - Webster
Word - A "speech sound" that comnicates a meaning

Based on that defanition, "Modding" is a word. Most of us have an understanding of what is meant when we see the word. Since the English laguage is a "living language" we can add words to it as long as they comunicate.
The other meaning of "modding" to me is modifying a computer but I can remember seeing it used 30 years ago when I sold pLastic models. There was always talk of "modding" a tank from one Version to another.