impossible figure

noun

a picture of an object that at first sight looks three-dimensional but cannot be a two-dimensional projection of a real three-dimensional object, for example a picture of a staircase that re-enters itself while appearing to ascend continuouslyAlso called: Escher figure

Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012