What does "unborder" mean?

To remove a border or borders from.

Unborder

verb

verb ·Rare ·Advanced level

Verb

1
To remove a border or borders from. rare, transitive
"Highlight the picture in question by giving it a border. Don't foget ^([sic]) to "unborder" the others."

"Highlight the picture in question by giving it a border. Don't foget ^([sic]) to "unborder" the others."

From un- + border.