Ronda Rousey -- Here's Why I Trashed Mayweather (Video)

Ronda Rousey says her ESPYs shot at Floyd Mayweather had been locked and loaded for more than a YEAR -- telling TMZ Sports she's been plotting against the boxer ever since he dissed her last year.

Ronda says Floyd had gotten snarky with her at the ESPYs last year -- when he claimed he had never heard of the UFC fighter. That was enough to piss off Rousey.

So, when she got the chance to fire away at Floyd, she took it.