redskirt

Etymology
. Patterned after, which derived from the tendency for male security officers, who wore red shirts, to die on episodes of Star Trek: The Original Series. Female crew members wore minidresses, but only one red-uniformed female character was killed during the series' run, in the episode "By Any Other Name."

Noun

 * 1)  An unimportant or expendable female character, especially one introduced only to be killed in order to underscore the peril faced by important characters.