That's pretty much the worst way I've heard to describe/define music.
*sigh... someone's a little discussion-mode, today.
It's actually a great definition, if you're into music and you know what you're listening...
Okay, here you go, mister
Nu metal uses "uncommon" tuning, a lot of songs tuned in D, B or even A. Almost all bassist uses 5-string bass guitars, because they use low notes in their songs.
The fusion thing is true, but that's really not accurate, you can try harder than quote wikipedia, it's true it has a lot of alternative metal, but it also has a lot of 90s thrash metal, if you hear Anthrax's song "Only", it has a really nu-metalish sound in the guitars and the voice-line (not the vocals, though).
The distorted guitars have special distortions, not the common heavy-thrash metal ones. In other words, they use the most sick and agressive distorsion.
The wah-wah harmonics (sorry, are they called like that in english? here they're "Artificial harmonics") are used A LOT, specially to create a mix between low-note riffs and high-pitched sounds mixed together.
Bass-guitar has a lot of more work than in thrash metal, bands like Limp Bizkit for example use high-pitched notes in the bass guitar during the verses and song's hooks, a little jazzy if you ask me.
Drumming is also agressive, similar to thrash and groove metal but with more unique "Ways to play it" (this is difficult to me to describe, i'm not a drummer, but I can try), let's call it "irregular" and with the drums not only as a base for the other instruments (like in some 80s metal), it has a lot more of participation in nü metal, making his own way through the songs.
Vocals use a lot of gutural sounds, the "Groovy voice" is also present, but it also has high pitched 70s-metal voices, and the first origins of screaming as we know now. A lot of rapping is accepted here too, but also melodic voices like Tankian.
You can combine those vocal skills and have a gutural-rap.
You mentioned Rage Against the Machine earlier, they're one of the first bands that made a sound similar to nü metal in their first album, I'd say they're the first "Early nu metal" band here, their combination from Alternative-Rap metal is probably one of the most influential band of that time.
You can add a lot of stuff in nu metal, every weird instrument can fit really good, look at Korn for example. Bands like Limp Bizkit or Linkin Park, who I consider the most pop-form of nü metal (of course we're talking about their 2 first albums, the next stuff is just pop-rock) uses DJs as band members and bring that stuff to every song.
Ok, I think I said enough.
Are you happy, now? I can continue if you want.