2 verb
border2 [transitive]
1SGP if one country, state, or area borders another, it is next to it and shares a border with it:
countries that border the Mediterranean
border on
The area borders on the Yorkshire Dales.
2 to form a border along the edge of something:
a path bordered by a high brick wall

border on something

phrasal verb
to be very close to being something extreme:
His confidence bordered on arrogance.

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