border line

US: (bôr′dər līn′)

WordReference Random House Unabridged Dictionary of American English © 2026

bor′der line′, 

1. boundary line;
   frontier.

• 1865–70

bor•der•line  (bôr′dər līn′), adj. 

1. on or near a border or boundary.
2. uncertain;
   indeterminate;
   debatable:
   not an alcoholic, but a borderline case.
3. not quite meeting accepted, expected, or average standards.
4. approaching bad taste or obscenity:
   He made several borderline remarks that offended them.

n. 

5. Psychiatry a person suffering from borderline personality.

• border + line¹ 1865–70

Synonyms

• 3. marginal, problematic, uncertain, doubtful.