Bongard problem

Etymology
After their inventor, the Russian computer scientist Mikhail Moiseevich Bongard (Михаил Моисеевич Бонгард, 1924—1971).

Noun

 * 1) A kind of puzzle in which there is one common factor in a first set of diagrams that is missing from a second set. The solver (possibly a computer program) must identify this factor.