Mostly a name for modern practical self-defense systems, which are founded after WWII in western countries as a combination of Judo, Karate and Aikido, specialized to use it against modern day attacks. Synonymous words like Jujitsu,
Ju-Jitsu or Ju-Jutsu are widely used.
Also name of a combination of western boxing and
wrestling with self-defense "tricks", brought from Japan to Europe and the US around 1900 to 1920. In later years often practiced as a companion to judo or as "judo self-defense" until the modern systems were founded. This Jiu-Jitsu often was presented in film,
e.g. in the Mr. Moto movies (starring Peter Lorre).
Self-defense arts called Jiu-Jitsu should not be mistaken with ancient
Japanese Jujutsu styles, which are traditional, classical bujutsu (martial skills) of the
Japanese warriors (samurai) and are in fact koryu (ancient budo). They have not much in
common with the Jiu-Jitsu we know.