1.VerbTo become involved in a situation, so as to alter or prevent an action. .mw-parser-output .object-usage-tag{font-style:italic}.mw-parser-output .deprecated{color:var(--wikt-palette-grey-lime-8,olivedrab)}[with in]
"The police had to be called to intervene in the fight."
2.VerbTo occur, fall, or come between, points of time, or events.
"An instant intervened between the flash and the report."
3.VerbTo occur or act as an obstacle or delay.
"Nothing intervened to prevent the undertaking.; The weather intervened before the contest could get under way."
4.VerbTo say (something) in the middle of a conversation or discussion between other people, or to respond to a situation involving other people.
5.VerbTo come between, or to be between, persons or things.
"The Mediterranean intervenes between Europe and Africa."
6.VerbIn a suit to which one has not been made a party, to put forward a defense of one's interest in the subject matter.
"an application for leave (i.e. permission) to intervene"