Charlie Sheen Rips Rihanna Yes I AM a Queen ... The Queen of Mean

5/22/2014 11:11 AM PDT

is in over her head -- Charlie Sheen has just issued a biting response to the singer's "queen" jab ... mocking her subpar command of the English language.

Charlie issued the response to TMZ in (what else) poem format:

"Dear Ms. Rihan-
  oh wait, no last name,
  Okay, Dear R -
clearly English is NOT
your primary language.

Firstly I want to thank you for recognizing me as Royalty. I'm flattered.
And secondly;
do the good Queen a favor and go tend to the dungeon in my Castle.
But beware of the
rats and the snakes.
They stir with folly
awaiting your tepid advance,
in the shadows..."

later Doosh!

As we reported, Rihanna tried returning fire after Sheen's anti-Rihanna tirade earlier today -- calling Sheen an "old queen" with his diapers in a bunch.

It's unclear if Rihanna was being homophobic, but "queen" is commonly a pejorative term for gay people ... and Rihanna's been in trouble before for allegedly bashing gays ... so we gotta ask ...