vanishing point

plural vanishing points

1. The point in a perspective drawing at which parallel lines receding from an observer seem to converge.

   These formulae . . . give for the vanishing point of a set of parallel lines whose common azimuth is α and declivity δ: η=d tan α, ζ=d tan δ sec α.

   1884, Wm. M. Thornton, “Construction of Perspective Projections”, in The Annals of Mathematics, volume 1, number 1, page 13

2. The situation in which, place where, or point in time when some object or phenomenon is no longer observable or notable.

   It might cut the tuberculosis deathrate to the vanishing point.

   1923 June 25, “Tuberculosis at Bay”, in Time

   2 more examples

   At 8h 35' 4", the least dent possible, quite black, appeared in the sun's limb. And at 8h 35' 6", the limb was restored to its perfect form, there having been a small trembling light, between the narrow watery border of Venus and the vanishing point of contact in the sun's limb for these two seconds of time.

   1762, Samuel Dunn, “Some Observations of the Planet Venus, on the Disk of the Sun, June 6th, 1761,”, in Philosophical Transactions (1683-1775), volume 52, page 192

   It hit 100 m.p.h. with ease and sped toward the vanishing point down Highway 93A.

   2003 August 25, Sally B. Donnelly, “The Need for Speed”, in Time