a geometric illusion in which two lines of equal length appear unequal depending on whether angular lines forming arrowheads at each end point toward or away from each other.
Origin: after Franz-Karl Müller-Lyer (1857–1916), German sociologist, who described the illusion in 1889
[muhl-er-lahy-er, myoo-ler-, mil-er-; Ger. myl-uh
r-lee-uh