ASYMPTOTE
asymptote
(noun) a straight line that is the limiting value of a curve; can be considered as tangent at infinity; “the asymptote of the curve”
Source: WordNet® 3.1
Etymology
Noun
asymptote (plural asymptotes)
(analysis) A straight line which a curve approaches arbitrarily closely, as they go to infinity. The limit of the curve, its tangent "at infinity".
(by extension, figuratively) Anything which comes near to but never meets something else.
Verb
asymptote (third-person singular simple present asymptotes, present participle asymptoting, simple past and past participle asymptoted)
(analysis) To approach, but never quite touch, a straight line, as something goes to infinity.
Source: Wiktionary
As"ymp*tote, n. Etym: [Gr. Symptom.] (Math.)
Definition: A line which approaches nearer to some curve than assignable
distance, but, though infinitely extended, would never meet it.
Asymptotes may be straight lines or curves. A rectilinear asymptote
may be conceived as a tangent to the curve at an infinite distance.
Source: Webster’s Unabridged Dictionary 1913 Edition