Noah Webster's New International Dictionary of the English Language

1. (v. i.) To interfere; to come between, or to be between, persons or things; -- followed by between; as, the Mediterranean intervenes between Europe and Africa.

2. (v. i.) To occur, fall, or come between, points of time, or events; as, an instant intervened between the flash and the report; nothing intervened (i. e., between the intention and the execution) to prevent the undertaking.

3. (v. i.) To interpose; as, to intervene to settle a quarrel.

4. (v. i.) 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.

5. (v. t.) To come between.

6. (n.) A coming between; intervention; meeting.