mas·ter·piece 
(măstər-pēs′)
(măstər-pēs′)n.
1. An outstanding work of art or craft.
2. The greatest work, as of an artist. Also called masterwork.
3. Something superlative of its kind: a masterpiece of political ingenuity.
[Probably translation of Dutch meesterstuk or German Meisterstück : Dutch meester and German Meister, master + Dutch stuk and German Stück, piece of work.]