The phrase "eastern border" refers to the line that separates a region or country from its neighboring area to the east. It marks the outer limits or boundary of that particular place towards the east side. Full definition
The Likud platform, Netanyahu's political party, explicitly rejects a Palestinian state and calls for the Jordan River to be «the permanent eastern border of the State of Israel.» (globaleducationmagazine.com)
2 - Storey concrete structure is built on a parcel measuring 60 ft. x 120 ft. located in the Duty Free Corozal Free Zone at the South Eastern Border with Mexico (Chetumal) (belizerealestate.bz)
The report identified five sites spread across three villages in Changbai County and two cities in the north - eastern border province of Jilin, which have been earmarked as camp locations. (fortune.com)