(n.) A passing or running between; occurrence.

encroachment entrance entrenchment impingement imposition incursion infiltration influx infringement injection inroad insinuation interagency intercession intercurrence interference interjacence interjection interlocation interloping intermediacy intermediation interposition interposure interruption intervenience intrusion invasion involvement irruption mediation obtrusion sandwiching stepping in trespass trespassing unlawful entry