The actual term for the definition below is ronin
. Rurouni is a word created by Nobuhiro Watsuki for the manga-turned-anime Rurouni Kenshin
The novel, The Story of the 47 Ronin, is based upon the deeds of 47 ronin (masterless samurai) otherwise known as the ex-samurai of Ako, at the beginning of the 16th century.
It is a common error to equate rurouni to ronin.