Most of my friends and I have a different (unspoken) value system on BBs (and I guess other belts too; like brown&purple). i.e. if Mike Brown says to me "Oh that guy's a BB" I'm like oh ok no big deal I'll roll with him, and I expect to tap him or to see Mike tap him. On another note if Mike says "That guy is a legit BB" I think to myself "This is going to be fun, I get to test myself and probably learn something or get some good pointers here. I still try to tap the guy, but I don't ever remember tapping a "Legit" black belt. Does everyone that trains understand/use this unspoken value?
P.S. "Legit" is also interchangeable with "High level".
Very good question, although I suck so bad off my back I have no place questioning anyone's legitimacy.
Yes, I think that's common.
It's like the difference between being just gay and being super gay.
Edit: Just to clarify, I'm not saying being a BB has anything to do with being gay. Just comparing the usage as being similar to when you say someone is gay vs. super gay. If you have any gay friends, you know what I'm talking about.
Also, as a person of no particular BJJ skill, I'm impressed when I hear either. But the "legit" part implies that they actively train and have competed enough to know they are solid.
When it's time to come on...
I take off my sunglasses and come on!!! 
Yves Edwards - Most of my friends and I have a different (unspoken) value system on BBs (and I guess other belts too; like brown&purple). i.e. if Mike Brown says to me "Oh that guy's a BB" I'm like oh ok no big deal I'll roll with him, and I expect to tap him or to see Mike tap him. On another note if Mike says "That guy is a legit BB" I think to myself "This is going to be fun, I get to test myself and probably learn something or get some good pointers here. I still try to tap the guy, but I don't ever remember tapping a "Legit" black belt. Does everyone that trains understand/use this unspoken value?
P.S. "Legit" is also interchangeable with "High level".
Yeah, sort of.
We say Legit for someones who good and clearly well deserving. So you could say high level...
What about illegitmate BBs?
Usually just say "academy BB" or "competition BB"
ttt
I'm legit
It's the same in MMA. We see "black belts" getting destroyed by purple let's regularly nowadays. Throw Charlie Oliveira in there with half of mma's "black belts" and see who gets tapped.
Random Guy From The Internet - I believe "legit" is a universal term.
I would have to agree. Al though, the only "legit" BB I have ever had the pleasure to be choked almost unconcious by was Fabricio Werdum. Sadly my school is no gi only so I wouldn't know what rolling with a low tier BB would be like.
minotauro11 - It's the same in MMA. We see "black belts" getting destroyed by purple let's regularly nowadays. Throw Charlie Oliveira in there with half of mma's "black belts" and see who gets tapped.
And Jim Miller rolled up Olivera and subbed him out without breaking a sweat.
Yeah man, it's like if someone says to me "that guys a shitty white belt" I'm like alright, I might have a chance against him, lets do this. But if they just tell me "this guys a white belt," I'm like oh shit, I'm gonna be in for a long 5 minutes.
tjmitch -minotauro11 - It's the same in MMA. We see "black belts" getting destroyed by purple let's regularly nowadays. Throw Charlie Oliveira in there with half of mma's "black belts" and see who gets tapped.
And Jim Miller rolled up Olivera and subbed him out without breaking a sweat.
A better example for me would be Lauzon vs Ruediger. but in mma all sorts of factors apply
Thanks guys, I always thought these terms were pretty much universal, but when I said it to a buddy today he was like a BB is a BB and I was like, you can keep thinking that if you like being wrong.
Yves
I think there universal. Kind of an unfortunate misnomer though as it sort of implies something illegitimate about the regular BBs. But inside bjj circles I don't think anyone means any disrespect. Let's face it. Some of these elite guys are amazing both in skill and athleticism. Whereas any white belt who doesn't give up can becom a BB.
" Wanderlei is a black belt and damn good but Roger Gracie would roll him up and smoke him like a joint. 
"
LOL you just skipped about 3-4 tiers of black belt in between those two.
Wrap your mind around the demonstrable fact that Roger beats ELITE black belts(who themselves hose tons of very good and talented black belts) so badly that they have to point to parts on a doll to show the cops where he hurt them.
The best Ive ever heard it put in regards to the level Roger has reached compared to his peers:
"Roger can turn the world championship tournament of BJJ into a group therapy session, simply by walking through the door."
And MMA fighter training striking, wrestling and BJJ along with tons of strength and conditioning work, may eventually legit earn a BB. But theyre not going to ever roll at the level of elite world class pure BJJ players who spent all their training time on that alone.
They might "hang" no gi with some who they match up style wise favorable against. But not in the kimono going by real BJJ rules.
I can roll decently well with HW black belts no gi. Mostly depends on their game.
But a good purple gi specialist will have me spinning out of control Lesnar style trying to keep up with them as they undo their lapels and use them to saw me in half.
I dont have the time or the interest to spend to learn that kind of game.
Yves Edwards - Thanks guys, I always thought these terms were pretty much universal, but when I said it to a buddy today he was like a BB is a BB and I was like, you can keep thinking that if you like being wrong.
Yves
nah, you're absolutely right. a lot of guys have black belts and when someone says that they're a black belt, the first thing I think is "is he legit or did this guy pay good money for his grading?"
I'm a white belt in gi but have been training in no-gi for years and I've rolled with a couple of black belts who I handled. That's generally a rare thing though for me to hang with a black belt.
I think at your level, and at Mike Brown's level, "legit black belt" definitely means more than it does to me.
"Legit black belt" could mean nothing to a guy like Marcelo Garcia but to a guy like myself, it means a lot because if I can hang with them, they are certainly not legit.
There's a huge discrepancy between BB's (and every other belt too.)
What Yves is suggesting is right on point. I always break them down by either a gym/training belt or a competition belt.
A competition BB is someone you are going to find yourself in some precarious situations with, where you can't distinguish whose limbs are whose. A gym BB is usually technical and could easily teach BJJ with perfect form, however, when it comes to rolling just can't reach that "level."