Meaning of Desargues's theorem

Desargues''s the'orem

Pronunciation: [key]
— Geom. Geom.
  1. the theorem that if two triangles are so related that the lines joining corresponding vertices meet in a point, then the extended corresponding lines of the two triangles meet in three points, all on the same line.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.