Meaning of “border” - Learner’s Dictionary

border

verb [ T ] uk us /ˈbɔːdər/
EDGE

to form a line around the edge of something:

[ often passive ] The fields are bordered by tall trees.
NEXT TO

to have a border with another country:

[ often passive ] Spain is bordered by France and Portugal.

(Definition of “border verb” from the Cambridge Learner’s Dictionary © Cambridge University Press)