rhea red Share definition Flag the red stain, or spot, on the back of pants (or skirts and such) if a girl didn't have a pad/tampon on and leaked. The girl said to her friend, "Oh my gosh, look at her ass, she got a rhea red." rhea red by anonyguyX April 8, 2009 0 0 Get merch Get the rhea red mug. Buy Now — $32.95 See more merch