Usain Bolt's GF Half Naked & Heaven-Sent for Jamaican Carnival

Usain Bolt's smokin' hot GF has broken out a Victoria's Secret-esque wardrobe for Carnival in Jamaica, begging a very important question ...

WHY IS USAIN GRINDIN' UP ON OTHER WOMEN?!

Don't worry -- doesn't seem like Kasi Bennett's trippin' on Bolt breakin' it down others ... remember that legendary hall pass she allegedly gave him during the Olympics?

But if we were The World's Fastest Man, we'd get down to wherever the hell Kasi is ASAP -- 'cause ain't nothin' gonna top what we see here.

Interesting side note ... Bennett tagged Bolt in one of her pics -- in a, let's say, "unique" location -- but is she doing that 'cause he's there, or 'cause she wants his attention?

Whatever -- you got ours, Kasi.