Here's Shareef O'Neal busting out some insane alley-oop dunks ... courtesy of rap superstar Quavo

The Migos member lobbed up a pair of dimes for Reef before a pickup game on Friday -- and the 17-year-old threw it down hard both times, including a pretty sick reverse jam.

Quavo ain't half bad either -- in fact, the dude was a star athlete back in Georgia and balled out as the QB on his high school football team. 

As for Reef, he's already committed to U of Arizona.

Sucks for ASU.