borderline

border +‎ line

borderline (comparative more borderline, superlative most borderline)

1. nearly; not clearly on one side or the other of a border or boundary, ambiguous.

   He is borderline hypoglycemic and needs to monitor his sugar intake.

   I would rather hire a talented layman than a university graduate with borderline qualifications.

2. Showing bad taste.

   Your borderline remarks about my aunt's dress destroyed my evening.

3. Exhibiting borderline personality disorder.

• borderline case
• borderline personality disorder

borderline (plural borderlines)

1. A boundary or accepted division; a border.

   She lives on the borderline between reality and madness.

2. An individual who has borderline personality disorder.
   • 1995, Eugene E. Levitt, ‎Edward Earl Gotts, The Clinical Application of MMPI Special Scales (page 80)

     As an example of their affective profile, borderlines are set apart from passive aggressives by having more marked social anxiety […] and greater sensitivity […]

borderline (third-person singular simple present borderlines, present participle borderlining, simple past and past participle borderlined)

1. (transitive) To border, or border on; to be physically close or conceptually akin to.

borderline m, f (plural borderlines)

1. (colloquial) Someone with borderline personality disorder