Samurai(from 1600-1868)who formally abolished their title for reasons varying from regret over those they had killed to the death of a master, lover or close friend. They rebuked their title and wandered around Japan with their swords, keeping them as grim reminders of their pasts. Often times they had no money and lived off the generosity of others.
Rurouni were frowned apon by the Shogunate
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.