Limitrophe: Situated on a border or along a boundary; Adjacent, bordering, or contiguous. Function: adjective. Etymology: French, from Late Latin limitrophus bordering upon, literally, providing subsistence for frontier troops, irregular from Latin limit-, limes boundary + Greek trophos feeder, from trephein to nourish. Date: 1763.
Usage in a sentence: "The area limitrophe to the river requires special vegetation treatments for environmental safety."
In the U.S., the Limitrophe is the segment of the Lower Colorado River that serves as the international boundary between the U.S. and Mexico.
From another dictionary, far less friendly to the eye, some etymology: limitrophe adj. on the frontier XIX; †sb. borderland XVI. — F. — late L. limitrophus , f. līmit - LIMIT + Gr. - trophos sup.