na-adjective, noun
Describes a person or behavior that is morally corrupt, depraved, or profligate. Often used in a dramatic or literary context.
彼は極道な生活を送っていた。
He led a wicked life.
あの男は極道だ。
That man is a scoundrel.
noun
organized crime; yakuza; underworld
Specifically refers to the yakuza or organized crime syndicates. Often used in news or crime-related contexts.
See also: ヤクザ
彼は極道の世界に足を踏み入れた。
He stepped into the world of organized crime.
ヤクザ is the more common and direct term for yakuza members or the organization. 極道 is a broader term that can also mean 'wicked' or 'scoundrel' in general, not limited to organized crime.
The term 極道 (ごくどう) originally comes from Buddhist terminology meaning 'the extreme path' or 'the ultimate way,' but in modern Japanese it has taken on the meaning of 'wickedness' or 'villainy.' The exact semantic shift is uncertain.