Gilbert Arenas is throwing some major salt in Nick Young's wounds -- clowning the guy for getting dumped by Iggy Azalea ... and he ain't pullin' any punches.
We THOUGHT the two were friends -- especially when Gilbert told us he had planned on going to Nick's bachelor party a few months back. But Nick wasn't having it and told him he wasn't invited.
Fast forward to last night ... after Gilbert found out Iggy broke up with Nick ... and Agent Zero unloaded on his former Washington Wizards teammate on the Gram.