encroachment

Short definition from Wiktionary

Noun

1. 1
   An entry into a place or area that was previously uncommon; an advance beyond former borders; intrusion; incursion.
2. 2
   An intrusion upon another's possessions or rights; infringement.
3. 3
   That which is gained by such unlawful intrusion.
4. 4
   An unlawful diminution of the possessions of another.