Shaquille O'Neal -- Shootout in Anguilla

Shaquille O'Neal has RETURNED to the basketball court ... in jean shorts ... in Anguilla.

It's actually a pretty cool story -- The Diesel was hosting a NYE party at the Viceroy on the Caribbean island, when he got on the mic and challenged everyone to a pick-up game at the hotel court the next morning.

Shaq kept his word ... and arrived ready to play ... with his GF in tow.

Sources at the court tell us, the NBA legend organized a friendly half-court shoot-a-round ... nothing too intense ... no dunking. Hoopz played too.

We're told Shaq was super friendly ... and posed for pics with anyone who wanted a shot.

As for Shaq's game -- we're told the guy actually looked pretty good ... sinking bucket after bucket.