Myles Garrett is officially done for the season ... and perhaps even longer.
The Cleveland Browns superstar was banned indefinitely by the NFL after he attacked Mason Rudolph with the Steelers QB's helmet at the end of "Thursday Night Football" last week.
But the 23-year-old met with league officials Wednesday (in his swaggiest blue outfit) with the hopes of getting the suspension reduced.
Turns out, the NFL wasn't buying what Garrett was selling ... and upheld the ban -- saying Garrett is still barred from the league for all of this season and maybe some of next.