Mojo.....I guess there's a bunch of different ways to describe the word. I'm guessing it means a certain bass has some *magical* quality apart from other basses of the same brand or type(?) I've played older, used basses that sounded great right off, others, maybe not so much. I've played new basses that sounded awesome right out of the gate. There's too many variables in my opinion, ranging from how the instrument is setup, the strings or amp it's being played through, how the amp is eq'ed, etc, etc,.
I've bought basses that at first, that didn't seem to be very special to me, but as I continued to play them, over months, somehow transformed into great basses. Maybe I varied it's setup, or tried a different type or brand of strings, or quite possibly I learned where the best places to pluck the strings to get what I was after out of it. I've heard some guys who can make pretty much every bass, through a less than stellar amp setup sound great. So I guess it's more in their hands, their overall technique.
I know this isn't the Amp's Forum, but I've played through many of the newer SVT setups, and I made them sound like crap, really generic, whereas almost everyone else I've heard playing through them sound fantastic. Many years back, when I played in a Club Band, we had a really good Soundman, who was also a good Rock Guitarist. He was like our 4th member, and was at all of our gigs. We would often have friends show up at gigs and sit-in on songs, and when it was a bass player, I'd sit with him at the P.A. Board. I would often comment to him that my bass sounded weak in the mix, he would always tell me that I would give him more of a signal, because I play with a heavier touch than the person that was playing my bass.
I've also experienced what other folks have already posted here while trying out a few of the same models of a bass in a music store. There would be that one that just sounded better to me than the others. But I'm sure that someone else trying the same basses out might choose a different one of the same basses as their favorite.
There's my long winded thoughts.