I. ˈ ̷ ̷ ̷ ̷ˌ ̷ ̷ adjective
1. : situated at or near a border line
a borderline town
2.
a. : situated between two points or states : intermediate
mental borderline states between dream and wakefulness — Jósef Wittlin
b. : verging on one or the other place or state without being definitely assignable to either one : marginal
a borderline district that was neither opulent nor impoverished
especially : not quite average, standard, or normal
a person of borderline intelligence
c. : not quite meeting or conforming to accepted patterns (as of good taste or morality) ; especially : verging on the indecent or obscene
a borderline joke
a borderline book
d. : not clearly fixed or convincing : subject to challenge or debate : dubious , questionable
in their opinion the new theory is of borderline validity
e. : manifesting typical but not altogether conclusive characteristics : apparently existent but lacking definitive development
a patient with borderline diabetes
attempting some sort of borderline economy
II. adjective
: characterized by psychological instability in several areas (as interpersonal relations, behavior, mood, and identity) often with impaired social and vocational functioning but with brief or no psychotic episodes
a borderline personality disorder
III. ˈ ̷ ̷ ̷ ̷ ˌ ̷ ̷ adverb
: not actually but very close to being : almost
is borderline senile