Synonyms of borderline in English:

borderline


See US English definition of borderline

See UK English definition of borderline

See Spanish definition of frontera

noun

1‘the item is on the borderline between being old and antique’

SYNONYMS
dividing line, divide, division, demarcation line, line of demarcation, line, cut-off point
threshold, margin, fringe, limit, border, boundary, periphery

adjective

1‘the moderators discussed student grades and borderline cases’

SYNONYMS
marginal, indefinite, uncertain, unsure, unsettled, undecided, up in the air, doubtful, open to doubt, problematic, indeterminate, unclassifiable, ambivalent, equivocal
questionable, open to question, disputable, debatable, arguable, controversial, contentious, moot
informal iffy
British informal dodgy