1Attributive and in the genitive. Designating or relating to an optical illusion in which a line with a V-shaped arrowhead pointing outward at each end appears shorter than an adjacent line of equal length with the V-shaped arrowheads pointing inwards.
2The Müller-Lyer illusion.
Late 19th century; earliest use found in The Philosophical Review. From the name of Franz Carl Müller-Lyer, German sociologist and psychiatrist, who described the phenomenon in Arch. f. Anat. u. Physiol.: Physiol. Abth Suppl. 263–70.