出典:Wiktionary
red + shirt. Derived from the red jersey commonly worn by a player meeting this definition in practice scrimmages against the regulars.
redshirt (三人称単数 現在形 redshirts, 現在分詞 redshirting, 過去形および過去分詞形 redshirted)
red + shirt. From the tendency of red-shirted ensigns in the Star Trek: The Original Series television program to die prematurely.