(cytology) red blood cell

(historical) a French revolutionary during the French Revolution / (historical, by extension) any revolutionary

(cycling) a red flag indicating to riders that the finish line is coming up in one kilometre

(astronomy) red dwarf (small, relatively cool star of the main sequence)

Red Crescent (humanitarian organization)

Red Cross (humanitarian organization)

(figuratively) in the red, overdrawn

European robin

European robin

lipstick (make-up for the lips)