Ex-WWE star Ryback is threatening a legal war with Ezekiel Elliott ... claiming the Cowboys player has NO RIGHT to get a "Feed Me" trademark -- despite the RB's new tat.
"I'll tie him up for years," Ryback said this week. "He ain't using it. So he better get a good tattoo artist to go have him cover that sh*tty tattoo up on his stomach."
If you're unfamiliar, Ryback popularized the phrase "Feed Me More" during his time in the WWE -- and it became so big, crowds chanted it at arenas for YEARS.