To become involved in a situation, so as to alter or prevent an action.
To occur, fall, or come between, points of time, or events.
To say (something) in the middle of a conversation or discussion between other people, or to respond to a situation involving other people.
To come between, or to be between, persons or things.
In a suit to which one has not been made a party, to put forward a defense of one's interest in the subject matter.
To occur or act as an obstacle or delay.
Synonym of stick one's oar in (“to interfere”)