(law) a proceeding that permits a person to enter into a lawsuit already in progress; admission of person not an original party to the suit so that person can protect some right or interest that is allegedly affected by the proceedings; "the purpose of intervention is to prevent unnecessary duplication of lawsuits"
the act of intervening (as to mediate a dispute)
a policy of intervening in the affairs of other countries
the entrance (the space in a wall) through which you enter or leave a room or building; the space that a door can close; "he stuck his head in the doorway"