(cytology) An erythrocyte (red blood cell).

(Internet, Wiktionary and WMF jargon) A red hyperlink that directs to a nonexistent page of a wiki.

(American football) The area extending twenty yards from the end zone, where a team in possession of the ball is expected to score.

Alternative spelling of blood red

(hematology, cytology) A type of cell in the blood of vertebrates that contains haemoglobin and transports oxygen from the lungs to the tissues; a red blood cell.

(chiefly Southern US) An earthworm.

A glycoside obtained from beets and used as a food dye, also known as betanin and E162.

plural of red corpuscle

(figuratively) A boundary or limit which should not be crossed. / (ice hockey) The thick red line on the ice which divides the rink in half.

(Canada, slang) Any of the red-painted electrical streetcars and subway trams operated by the Toronto Transit Commission in Toronto, Canada, especially the classic models used during the early and mid-20th century.