Shaq -- RAP AUDITION FOR PHARRELL ... Put Me On the NBA 2K15 Soundtrack!!!

Shaquille O'Neal wants to get BACK IN THE RAP GAME ... for real ... and he's so serious, he just made a freestyle rap audition video for Pharrell.

Despite the fact it's been 16 years since The Diesel released his last album, Shaq is hittin' up the "Happy" singer to give him a chance to rap on the NBA 2K15 video game soundtrack (which P is producing).

Hence the audition video ... in which Shaq rhymes the work "platinum" with ... well, we really can't understand what he's saying ... it's sorta gibberishy.

While the freestyle isn't quite on "Tell Me How My Ass Tastes" levels of epicness, it's not far off. Check it out.

FYI -- Nothing will ever be on "Tell Me How My Ass Taste" levels ... Nothing.