A word meaning “drifter”. Historically, a Samurai who had lost, abandoned, or had been abandoned by their master during the feudal era of Japan. Media examples could be found in Samurai 7, Jinnosuke from Samurai Champloo, and more famously, the title character Himura Kenshin from Rurouni Kenshin. The word is also currently used in Japan to designate students who have failed their college entrance tests and spend their time studying in order to retake them.
A character class in several games such as Disgaea, Disgaea 2, Makai Kingdom and the western name for Sekaiju no Meikyuu/Etrian Odyssey's Bushidou. Whereas the Makai Kingdom and Disgaea 2 classes are easy to distinguish, there is some confusion between the other two as they seem nearly identical at first glance. A simple way to tell them apart is to look for the armor plates the Sekaijuu ronin wear in their arms, which are absent from the Disgaea variant, and more reliably, as the armor is sometimes missing in the former as well, the color of the knot in their hair (Red for Sekaiju, white for Disgaea). More generally, the Sekaijuu versions are usually depicted as smaller and flat-chested (Though there are exceptions), and they do not wear the hakama over their upper bodies.