A derivative from
word "retard".
A
person who is subscribed to /r/traa subreddit on
Reddit and loudly voices their subjective opinion on other subreddits, usually an SJW.
Some
guy: His name is Felix. And it's a guy.
Other dude: No her name is Ferris and she is
female.
Some guy: Other dude, are you a rtraard? Everyone here knows that Felix from Re:
Zero is a dude.