Fermat's last theorem

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun The theorem that the equation aⁿ + bⁿ = cⁿ has no solutions in positive integers a, b, c if n is an integer greater than 2. It was stated as a marginal note by Pierre de Fermat around 1630 and not proved until 1994 by the British mathematician Andrew Wiles (born 1953).